The reported movement of 80,000 BTC that had remained dormant for years has revived a difficult legal question: can Bitcoin adverse possession exist? In other words, can someone acquire ownership of allegedly abandoned crypto-assets simply because time has passed?
It is an attractive question, but it should not be answered too quickly.
Under traditional civil law, adverse possession or acquisitive prescription can allow ownership or certain property rights to be acquired when strict legal requirements are met. Blockchain creates a different problem: there is no physical land to occupy, no tangible object to hold and technical control of a private key does not always match legal ownership.
For companies, investors, custodians, family offices and technology projects, this is not theoretical. It affects how digital assets are documented, how private keys are held, how internal protocols are designed, how digital inheritance is handled and how disputes over crypto-assets are resolved.
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The case: old wallets, on-chain notices and a classic property law question
The debate was triggered by reported movements of significant amounts of Bitcoin that had been inactive for years. In parallel, the crypto community has discussed messages inserted into the Bitcoin blockchain through OP_RETURN, a function that allows data to be included in a transaction and publicly recorded.
According to sector reports, some of those messages had the appearance of legal notices addressed to old or inactive wallets, raising concepts such as abandonment, constructive possession and possible claims over digital assets.
The idea is legally provocative: using the blockchain itself as a notice board, creating a public, traceable and verifiable communication addressed to a wallet.
But an on-chain notice does not automatically make the sender the owner.
That is the key point for companies: blockchain can provide evidence, but it does not replace the legal analysis of title, contracts, inheritance, custody, liability, fraud prevention or proof of ownership.
What adverse possession requires
In Spanish law, the Civil Code allows ownership and other rights in rem to be acquired by prescription, but only under the conditions established by law.
Possession must be in the capacity of owner, public, peaceful and uninterrupted. Ordinary acquisitive prescription also requires good faith and valid legal title.
For movable property, Spanish law provides rules based on uninterrupted possession for three years with good faith or six years without requiring another condition. However, applying those rules to Bitcoin requires answering several prior questions:
- what exactly is the legal object in a crypto-asset;
- what it means to possess an asset controlled through private keys;
- against whom that possession is exercised;
- which law applies;
- what evidence proves ownership;
- whether there is good faith;
- whether there is valid title or another legal basis for control.
The analysis cannot be reduced to the phrase “whoever has the private key owns the asset”.
Technical control is not always legal ownership
In crypto, a practical rule is often repeated: whoever controls the private key controls the asset.
As a technical rule, that is useful. As a legal conclusion, it is incomplete.
A private key allows transactions to be signed and funds to be moved. But that technical power does not necessarily prove that the person moving the funds is the lawful owner. There may be:
- custody on behalf of another person or company;
- a management mandate;
- a deposit arrangement;
- pending inheritance;
- a corporate structure;
- a multisig wallet;
- operational access held by an employee or provider;
- loss or recovery of a seed phrase;
- misappropriation;
- unauthorised access;
- key theft or fraud.
For a company, the practical consequence is clear: if crypto-assets have material value, ownership should not depend only on whether someone can sign a transaction.
There should be legal, accounting, corporate and technical documentation explaining who owns the asset, who holds custody, who may operate it, under what limits and what happens in a crisis.
A dormant wallet is not necessarily an abandoned wallet
One serious mistake would be to equate inactivity with abandonment.
The fact that a wallet has not moved funds for ten, twelve or fifteen years does not prove that the owner has given them up. It may reflect cold storage, a long-term investment strategy, inheritance planning, a reserve wallet, temporary loss of access or an operational block.
Nor is it enough for a third party to publish a blockchain notice and treat silence as a waiver of rights.
An on-chain message can be an interesting piece of evidence. It may help show that someone attempted to notify, warn or create a record. But it does not automatically transfer ownership.
The main legal obstacles
1. The legal object
Bitcoin and other crypto-assets are not traditional tangible things. MiCA defines a crypto-asset as a digital representation of a value or a right that may be transferred and stored electronically using distributed ledger technology or similar technology.
That regulatory definition is useful, but it does not solve every private law question about possession, title, recovery claims or adverse possession.
2. Possession
With land, possession may be shown through occupation, use, maintenance or exclusion of others. With jewellery or a vehicle, physical possession is often visible.
With Bitcoin, “possession” is often confused with key control. But that control may be lawful, delegated, shared, accidental or unlawful.
Any adverse possession argument would therefore need to explain how possession occurred, since when, with what publicity, against whom and in what capacity.
3. Good faith
Good faith is one of the most sensitive points. Anyone claiming rights over another wallet would need to explain why they believed they had a legitimate basis to possess or acquire the asset.
If access came from an unauthorised key, a security breach, credential appropriation or phishing, the discussion may quickly move into criminal liability, civil liability or contractual breach.
4. Valid title
For ordinary acquisitive prescription, title must be real, valid and proven. Under Spanish law, valid title is not presumed.
For crypto-assets, this means documenting the origin of ownership: contracts, purchase records, corporate resolutions, investment agreements, custody mandates, exchange records, tax evidence, internal approvals, signing instructions or inheritance documents.
5. Applicable law
Bitcoin has no obvious physical location. A single dispute may connect to several jurisdictions: the owner’s residence, the company’s registered office, the custodian’s location, the exchange’s terms, governing law clauses, inheritance rules, AML obligations or insolvency proceedings.
Blockchain is global, but property disputes are still decided within specific legal systems.
Three scenarios companies should distinguish
Scenario 1: the legitimate owner is creating evidence
The owner may move funds, sign a message or perform an on-chain transaction to evidence control, continuity or ability to dispose of the asset.
For older acquisitions where banking, contractual or tax records may be incomplete, on-chain evidence can be relevant. It should still be supported by off-chain documentation.
Scenario 2: a third party has partial legitimate access
An administrator, shareholder, trustee, employee, heir, technology provider or custodian may have operational access to a wallet without full ownership of the assets.
This often leads to corporate, inheritance, employment, contractual or professional liability disputes.
Scenario 3: a third party tries to turn control into title
This is the most delicate situation. If someone obtains access to a wallet without sufficient legal basis and then tries to justify that position through abandonment, constructive possession or prescription, a company should quickly assess:
- origin of access;
- traceability of movements;
- ownership documentation;
- potential liabilities;
- interim protective measures;
- communications with custodians, exchanges or authorities;
- litigation and evidence strategy.
What companies holding crypto-assets should review
The adverse possession debate teaches a practical lesson: self-custody without a legal structure can become a serious asset protection problem.
Companies holding or managing crypto-assets should review:
- wallet and asset inventory;
- legal owner identification;
- custody policy;
- access rules for private keys;
- multisig wallet governance;
- contracts with custodians or technology providers;
- acquisition documentation;
- accounting and tax treatment;
- powers and internal authorisations;
- contingency protocols;
- business or family succession;
- response plans for lost keys;
- available on-chain and off-chain evidence.
The key is not only being able to move funds. The key is being able to explain legally why the company is entitled to move them.
Conclusion: adverse possession enters the blockchain debate, but not as a shortcut
The main lesson is not that a Bitcoin wallet can already be acquired by adverse possession. The lesson is more nuanced: traditional property law concepts will increasingly be used to resolve disputes over digital assets.
Possession, abandonment, valid title, good faith and proof of ownership do not disappear because an asset is on a blockchain. But they cannot be applied mechanically as if a wallet were land, jewellery or a vehicle.
With crypto-assets, the private key gives control. The law determines whether that control is justified.
Auratech Legal helps companies, professional investors and technology projects structure crypto-asset custody, document ownership, prepare access protocols, review contracts with technology providers and design legal strategies for disputes involving wallets, private keys or digital assets.
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FAQ
Can Bitcoin be acquired by adverse possession in Spain?
There is no settled answer. Adverse possession exists under Spanish civil law, but applying it to Bitcoin requires analysing the object, possession, good faith, valid title, evidence and applicable law.
Does a dormant wallet mean the Bitcoin has been abandoned?
Not necessarily. Wallet inactivity does not by itself prove abandonment or waiver. It may reflect cold storage, long-term holding, inheritance planning, temporary loss of access or operational restrictions.
Does a private key prove ownership of Bitcoin?
It proves technical control, but not always legal ownership. Custody, mandates, deposits, delegated access, inheritance, corporate disputes or unauthorised access may all affect the legal analysis.
What should a company holding crypto-assets do?
Document ownership, regulate custody, define access rights, keep acquisition evidence, prepare contingency protocols and review contracts with custodians or technology providers.
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