blockchain
Distributed digital ledger whose legal significance depends on how it is used
Blockchain is a technical infrastructure based on a distributed digital ledger in which transactions and data are recorded in linked blocks. Each block contains information about preceding blocks through cryptographic hash functions, which makes it technically difficult to alter earlier entries without the acceptance of the network's participants. The technology operates in a decentralised manner without a central authority, and all participants have access to the same updated version of the ledger.
In a legal context, blockchain is not an independent source of law or a legal person, but a technology whose legal significance depends on how it is used. The technology is used for, among other things, cryptocurrencies, registration of ownership, smart contracts and documentation of transactions. Its decentralised nature means that data and transactions may be spread across several countries and jurisdictions at the same time.
There is no separate Danish or international statutory definition of blockchain as a technology. Instead, blockchain-related matters touch on different sets of rules depending on the specific application, including rules on electronic signatures, payment services, data protection, money laundering and the assessment of evidence.
The greatest legal challenge posed by blockchain in international law is the question of jurisdiction and choice of law. When transactions and digital assets exist across national borders without a physical location, complex questions arise as to which country's law applies and which courts have competence. This is particularly the case in disputes over ownership, breach of contract or crime related to blockchain-based systems.
In a criminal context, blockchain may be relevant both as evidence of transactions and as a tool for crime, for example money laundering through cryptocurrencies or trade in illegal goods on anonymous marketplaces. The pseudonymous nature of many blockchain systems can make investigation difficult, while the permanent record can at the same time give the police a detailed transaction trail.
