Blockchain lawyer in Paris: prove the transfer, enforce the contract.

It proves a fact: a transfer from one address to another, on a given date and for a given quantity. On its own, it says nothing about the reason for the transfer or about the identity of the people who control the addresses. Yet a person who asks for performance of an obligation must establish the act that gave rise to it, and not merely the movement of value. Facts may be proved by any means (Article 1358 of the French Civil Code). For a legal act whose value exceeds the regulatory threshold, a written document is in principle required (Article 1359 of the Civil Code). The Paris judicial court (tribunal judiciaire) points out that “proof of the handing over of funds to a person is not sufficient to justify that person's obligation to return the sum received” (our translation) (TJ Paris, 4th ch. 1st sect., 10 February 2026, No. 24/03591). A block explorer therefore shows the handover; the contract itself is proved by a written document, a corroborated commencement of proof or, between traders, by any means. The firm matches the history of the addresses, the exchanges preceding the transfer and any general conditions of the platform to reconstruct the agreement. It is this linking, and not the mere capture of a block, that allows the judge to characterise the transaction: loan, sale, deposit, investment mandate or a simple payment without consideration.

A public address can be read on the chain, but the link between that address, a customer account and a person is known only to the platform that holds the assets. Before any proceedings, the judge may order any legally admissible investigative measures if there is a legitimate reason to preserve or establish evidence of facts on which the outcome of the dispute depends (Article 145 of the French Code of Civil Procedure). Seised by a company that accused a former employee of diverting the payment of commissions to their own wallets, the Paris urgent applications judge held that “the claimant therefore has a legitimate reason to obtain the history of the transactions that took place on these wallets”, in order to allow it “to improve its evidentiary position with a view to the future trial” (our translation) (TJ Paris, réf., 5 November 2025, No. 25/55721). The measure was limited in time and in scope, and no legally protected secret stood in the way. The request must therefore be precise: the addresses concerned, the period, the type of information expected, and the link with the action envisaged. The firm first gathers the elements that make the case credible (invoices, reports, exchanges, statements) before filing the ex parte application or the summons for an urgent hearing, then uses the statements obtained to quantify the claim on the merits.

Yes, where the address is linked to an account opened with a provider that knows its customer. The Lyon judicial court, ruling in urgent proceedings, was seised by an individual who had filed a criminal complaint for fraud and had the path of their funds analysed as far as an address hosted by a platform. The platform, which intervened voluntarily, “does not deny that it holds the information making it possible to identify the holders of the exchange account” (our translation) (TJ Lyon, réf., 5 May 2025, No. 25/00185). The judge ordered it, subject to a daily penalty, to provide the information needed to identify the holders and their habitual residence, and temporarily to suspend their access to the services. This is an urgent-applications order made on particular facts, not a general rule: each request depends on the analysis report produced, the complaint, the proportionality of the measure and the court's jurisdiction over the provider. For a self-hosted wallet, the identity of the holder does not follow from the address alone: the link is sought in the exchanges with the person who supplied the address, in the path of the funds and in the information that providers through which the funds passed may hold. The firm examines these elements before choosing the civil route, the criminal route or both.

A loan is a legal act. Above the amount set by decree, it must be proved in writing (Article 1359 of the Civil Code), and the Metz court of appeal applies this threshold of €1,500 (CA Metz, 1st ch., 16 December 2025, No. 22/01436). Failing a proper written document, it may be replaced by a commencement of proof in writing corroborated by another element (Article 1361 of the Civil Code), that is, a document emanating from the opposing party that makes the allegation likely (Article 1362 of the Civil Code). In a case where funds had been handed over for cryptocurrency investments, the Paris judicial court ruled, on a typed acknowledgement of debt whose sum had not been written by the debtor herself as required by Article 1376 of the Civil Code, that “This document cannot therefore constitute proof of her undertaking. It does, however, constitute a commencement of proof in writing.” (our translation) (TJ Paris, 4th ch. 1st sect., 10 February 2026, No. 24/03591). The commencement of proof was corroborated by the borrower's complaint, an email and the bank statements, and the court ordered her to repay €130,000. The exception based on a moral impossibility of obtaining a written document (Article 1360 of the Civil Code) is assessed strictly: the Bordeaux court of appeal pointed out that “family or trust ties are not sufficient to justify the existence of a moral impossibility of obtaining a written document when the act was concluded” (our translation), and upheld the dismissal of a lender's claim (CA Bordeaux, 1st civ. ch., 27 March 2025, No. 22/04710). The firm lists the messages, transfers, statements and wallet addresses that may play this role.

Not always, and this is often where cases are lost. The Metz court of appeal refused to treat a €10,000 loan as established on the strength of screenshots that “do not make it possible to know with certainty the identity of their authors” (our translation), as no number or other element linked these messages to the defendant (CA Metz, 1st ch., 16 December 2025, No. 22/01436). The first-instance award was reduced from €13,000 to €3,000, the only amount supported by a document emanating from her. This decision went against the claimant: the screenshots produced made it possible neither to identify their authors with certainty nor to link the messages to the sum claimed. For an electronic document, the law sets precisely these two conditions: an identifiable person and a medium preserved in such a way that it cannot be altered (Article 1366 of the Civil Code). The firm recommends exporting the conversations from the application, keeping the metadata, having access to the account recorded by a commissaire de justice and, where a wallet address appears in the messages, matching it against the history of the chain. Several concordant indications are worth more than a single screenshot.

A report gives pages, a wallet or a block explorer a reliable date and description, provided it is carried out according to the rules. The Paris court of appeal points out that “Compliance with a number of technical prerequisites, intended to ensure the integrity of the findings made, is required of the commissaire de justice before drawing up the report recording findings on the internet” (our translation) (CA Paris, pôle 5 ch. 1, 17 June 2026, No. 24/07818). It lists the equipment used, the IP address, the browsing mode, the clearing of caches, cookies and history, the deactivation of the proxy and the annexing of the extractions. For a part of a report where these checks were missing, it upheld the exclusion, noting that “While this omission is liable to compromise the integrity of the information thus collected, justifying that page 5 of this report be excluded from the proceedings” (our translation) (CA Paris, pôle 5 ch. 1, 17 June 2026, No. 24/07818). It did, however, reinstate the pages reproducing messages that had already been loaded and could be read offline, which the first-instance judges had excluded. Before commissioning one, the firm therefore prepares the list of addresses, transaction identifiers and pages to be consulted, checks that the commissaire de justice works from their own computer and asks for the raw extractions to be annexed. A blockchain transaction lends itself well to this work: its identifier allows any third party, including the expert or the judge, to find the same entry and check the report.

Yes, if these messages contain the elements of the agreement and satisfy the conditions for an electronic written document. The Court of Cassation set aside a court of appeal decision that had refused to see a contract in a series of emails on the ground that they did not form a single document: in its view, “Article L. 222-17 of the Sports Code does not require the contract whose legal regime it lays down to be drawn up as a single written instrument” (our translation) (Cass. 1re civ., 11 July 2018, No. 17-10.458). It also rejected the idea that an electronic message could not, by nature, carry the parties' undertakings. The judgment concerned a written document required for the validity of that mandate. In matters of evidence, it is the law that sets the general rule: a dematerialised document has the same evidential value as paper provided that its author can be identified and its content is preserved without alteration (Article 1366 of the Civil Code). For a blockchain project, this means that the offer, the acceptance, the price in tokens or euros, the delivery address and the timetable may result from correspondence. It must still be possible to produce it reliably. For a contract signed online, the Rennes court of appeal relied on the signature provider's evidence file, corroborated by other documents, and noted that the debtor, who had defaulted, did not dispute their signature (CA Rennes, 2nd ch., 23 June 2026, No. 24/02562). The firm reconstructs the chronology of the exchanges, identifies the message that marks acceptance and checks that each essential element appears in it, before drafting a formal notice that refers to it precisely.

It is no longer excluded as a matter of principle. The plenary assembly of the Court of Cassation holds that “in civil proceedings, the unlawfulness or unfairness in obtaining or producing evidence does not necessarily lead to its exclusion from the proceedings” (our translation) (Cass. ass. plén., 22 December 2023, No. 20-20.648). If asked, the judge must check that production is indispensable to the exercise of the right to evidence and that the interference with the other party's rights is strictly proportionate to the aim pursued. The second civil chamber applied this review in approving a court of appeal that had admitted a recording made covertly, limited to the sequence of events, where the witnesses present depended on the employer (Cass. 2e civ., 6 June 2024, No. 22-11.736). For a blockchain transaction, the question arises with a call recording, access to a third party's account or the extraction of a shared messaging account. The risk remains: unfair evidence that is not indispensable, or whose interference is excessive, will be excluded, and obtaining it may have its own consequences. The firm always starts with the fair evidence available (the public history of the chain, a report, an investigative measure) and discusses producing a sensitive item only as a last resort, with the justification for its necessity.

The parties are bound by what they have agreed (Article 1103 of the Civil Code). Where the code was intended as a tool of performance, its operation does not by itself modify the obligations stipulated; it must still be checked what place the parties gave it in their agreement. If the written stipulations are clear, the judge cannot reinterpret them: it is forbidden to distort a clear and precise clause (Article 1192 of the Civil Code), and the Court of Cassation set aside a court of appeal decision, pointing out that “the lower courts may interpret agreements only if they are obscure or ambiguous” (our translation) (Cass. com., 13 May 2026, No. 25-10.491). Only where there is ambiguity does the common intention prevail over the wording (Article 1188 of the Civil Code). A mismatch between the deployed code and the contractual documentation is therefore treated first as a question of performance: did the programme do what the contract provided for. Where several documents coexist (general conditions, special conditions, white paper), the hierarchy between them matters; the law gives priority to the special conditions (Article 1119 of the Civil Code). The firm compares the written undertakings with the technical elements available, assesses whether an opinion from a technician on the deployed code is needed, then characterises the mismatch: performance error, non-performance, or an ambiguous clause to be interpreted.

First reread the agreement making the assets available, its general conditions and its special conditions, because the object of the return depends on them: the same quantity of tokens, or their counter-value on a given date. In a case concerning bitcoins lent for a guaranteed return, the Nice judicial court noted a contradiction between the two documents and held that “where the general and special conditions do not coincide, the latter prevail over the former” (our translation) (TJ Nice, 4th civ. ch., 14 November 2025, No. 24/01200). The return was due at the value on the day of the loan, with the interest promised. As the borrower had been placed in judicial liquidation and the attachments had proved fruitless, the court ordered the person who had undertaken that the contract would be performed (porte-fort) to pay, adding a loss of a chance linked to the rise in the exchange rate. The creditor has the remedies for non-performance: enforced performance, termination, compensation (Article 1217 of the Civil Code), and the debtor is ordered, where appropriate, to pay damages, unless there is force majeure (Article 1231-1 of the Civil Code). The firm checks each debtor's solvency, the security stipulated, the existence of insolvency proceedings and the rate applied, before sending the formal notice and choosing the court.

More freely than between individuals. As regards traders, commercial acts may be proved by any means, unless the law provides otherwise (Article L. 110-3 of the Commercial Code). The Court of Cassation pointed this out in a case concerning a guarantee given by a commercial company: “the guarantee in question being a commercial act, it may be proved by any means” (our translation) (Cass. com., 1 April 2003, No. 00-14.070). This judgment also shows the limit of the rule: the decision was set aside on another point, for lack of proof of the authority of the person who had bound the company. Freedom of proof therefore does not remove the need to establish who acted and with what authority. For services paid in tokens, an exchange of messages, an invoice mentioning an address, the history of the chain and the platform statements may together establish the agreement and the payment. Where the customer is an individual, the written-document rule regains its force against them. The firm therefore checks the status of each party, the nature of the act and the signatory's authority, before choosing the documents to produce and the competent court.

The ordinary limitation period for personal actions is five years (Article 2224 of the Civil Code). Its starting point is not necessarily the date of the transfer: it runs from the time the person knew, or should have known, the facts that allowed them to act. For a token loan, this will often be the missed return date; for a diverted payment, the discovery of the diversion. The timestamp of the chain helps precisely to date these events, which serves both the claim and the defence. But waiting is rarely useful. Platforms do not keep their customers' data indefinitely, funds move quickly, and an investigative measure before proceedings presupposes a dispute that is still credible (Article 145 of the Code of Civil Procedure). In the case decided in Lyon, the claimant, who had filed a criminal complaint in February 2024, issued a summons in January 2025 to obtain the identification of the holders and the suspension of access to the account where part of their funds had been located (TJ Lyon, réf., 5 May 2025, No. 25/00185). From the first contact, the firm draws up a dated chronology, transaction by transaction, and flags the steps that must be taken quickly: report, application, formal notice or complaint.