This doctoral dissertation analyses the civil-law structure and legal nature of the relationships that users enter into when using decentralised applications, with a focus on DeFi applications for lending and borrowing crypto-assets. The central theme is how to identify roles and legal relationships among the dispersed actors within the complex architecture of decentralised applications. The dissertation therefore does not treat smart contracts as a supposedly new type of contract in themselves. Instead, it starts from the question of which legal relationships smart contracts and decentralised protocols actually enable in practice, and how these relationships can be coherently classified within the framework of contract and obligations law.
The aims of the dissertation are: (1) to understand the effects of decentralised applications and smart contracts from a contract-law perspective, (2) to identify the relationships that are formed and performed through decentralised applications, and (3) to determine the circumstances that shape their legal nature and structure, while offering a general analytical framework for assessing concrete cases. The research is guided by three questions: (i) what is the legal nature of the relationships between users and other participants in decentralised applications, and on what does it depend; (ii) which types of contracts are concluded when decentralised applications are used, and between whom; and (iii) whether existing contract law provides an appropriate framework for understanding these relationships. On this basis, two hypotheses are formulated. Hypothesis 1 assumes that the structure and legal nature of these relationships are not uniform, but depend on the degree of decentralisation and the operational model of the application. Hypothesis 2 assumes that legal transactions on decentralised applications are valid only within a theory of abstraction between the obligatory (causal) transaction and the dispositive (transfer) transaction.
The dissertation is situated in civil law, primarily in the law of obligations, and uses a combination of source analysis and synthesis, a doctrinal (theoretical-logical) method when dealing with declarations of intent and legal transactions, a sociological method for identifying actual practices and relevant actors, and, in certain parts, a comparative method as support for more convincing explanations (not as a strict comparison of legal systems). An empirical study of user intent was abandoned due to pseudo-anonymity and the lack of a reliable central source. Instead, intent is reconstructed through users’ observable actions. The research field is deliberately limited to DeFi lending/borrowing applications on the Ethereum blockchain and to analysing the structure and legal nature of relationships (rather than their detailed substantive content), while public-law perspectives are intentionally kept in the background.
A key conceptual move is the analytical treatment of a blockchain transaction as a possible carrier of a declaration of intent. The dissertation finds that, by digitally signing a transaction, a user always expresses at least an intention regarding the legal act of executing the transaction (that is, an instruction to the network to execute it in accordance with blockchain rules). In addition, the same signature can (though not necessarily in every case) also express an intention regarding the underlying legal transaction, where the user pursues legal effects through the transaction (for example, a loan, a gift, and similar). This means that the link between the technological act (signing/executing a transaction) and its legal effect depends on the cause and content of the expressed intent, rather than on the technological form itself.
At the level of DeFi relationships, the dissertation shows that attempts at a single, “uniform” explanation (one scheme of contractual parties for all decentralised applications) fail to capture the diversity of real-world configurations. The degree of decentralisation has direct legal consequences because it affects whether a party on the “application side” can be identified as a bearer of rights and obligations. To identify a provider of financial services in operational terms, the dissertation develops a two-step test: first, whether there is “independent control” over the application (in the sense of influence over assets, access, or use), and second, whether the actor actually performs a financial service (including whether the actor’s service is necessary for the financial service, the actor’s influence on price and fee collection, and the ability to exclude users). This test is then used to assess the roles of protocol operators, interface providers, and other participants.
The dissertation systematises the research field into six types of DeFi applications, based on a combination of: (i) degree of decentralisation (on-chain CeFi vs pDeFi), and (ii) operational model (peer-to-peer, peer-to-pool, and peer-to-contract). For each type, it identifies the structure of relationships in relation to the underlying lending transaction. In on-chain CeFi (peer-to-peer and peer-to-pool), users do not conclude loan contracts directly with each other. Instead, the contractual relationship concerning the financial service is formed with an identifiable financial service provider (either the protocol operator or the interface provider, depending on the two-step test). In on-chain CeFi (peer-to-contract), users enter into a contractual relationship with the financial service provider specifically on the borrowing side, because there are no traditional lenders and the borrowed assets are generated when the loan arises. In pDeFi (peer-to-peer), because there is by definition no identifiable financial service provider on the application side, the loan contract is concluded directly between two users (lender and borrower), while users may at the same time enter into separate relationships concerning information society services with other actors (for example, an interface or protocol operator), but not as part of the loan relationship. In pDeFi (peer-to-pool), the borrower enters into the loan relationship directly with liquidity providers. The structure on the lender side can vary (separate relationships with each liquidity provider, a single joint relationship with all, or a relationship treating providers as a civil-law partnership), depending on the specific features of the application. In pDeFi (peer-to-contract), the “loan” relationship is qualitatively different: when borrowing, the user does not conclude a contract with anyone, but performs a sui generis unilateral legal transaction, whereby locking collateral creates a debt against the user’s own assets without the participation of a third party. This configuration is the clearest example of how the operational model of a pDeFi application can directly reshape the legal nature of the relationship.
Within this defined field and based on the synthesis above, Hypothesis 1 is confirmed: the legal nature and structure of the relationships are not uniform, but depend on the degree of decentralisation and (especially in pDeFi) also on the operational model of the application. Hypothesis 2 is rejected: the core reason lies in the doctrinal finding that blockchain transactions often (and in DeFi typically) also express intent regarding the obligatory legal transaction, so validity does not need to be explained through a strict requirement of an abstract separation between the obligatory and dispositive transactions.
The dissertation’s contribution is threefold: (1) it provides a doctrinally grounded model for understanding a blockchain transaction as a legal act, distinguishing (while also connecting) the intent to execute the transaction and the intent regarding the underlying legal transaction; (2) it develops an analytical tool (the two-step test) for identifying a financial service provider within the DeFi ecosystem; and (3) it systematises and comparatively describes the contractual structure of six categories of lending-type DeFi applications. In this way, the dissertation strengthens legal predictability and establishes a doctrinal basis for further debate (including regulatory debate), which would be methodologically risky without a prior reconstruction of the relevant civil-law relationships.
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