Western legal systems have historically helped establish trust between parties and reduce transactional uncertainty by providing recourse to legal procedures. Nonetheless, establishing trust still imposes significant transactional costs and blockchain may reduce them to a smaller level. In the meantime, the very nature of the technology raises fundamental questions about antitrust law and how individuals conduct transactions. This article intends to contribute to the literature by describing the challenges that blockchain presents for analyses of unilateral anticompetitive practices and proposing some changes to antitrust law and regulations that address those challenges. It proceeds in three sections to this end. First, this article argues that, because blockchain is decentralized, anonymous, and immutable, questions arise regarding the ability to detect anticompetitive practices and their perpetrators. We show that some practices are de facto more likely to be implemented. Next, this article discusses current antitrust laws and how antitrust authorities should tackle these issues. On the one hand, regulators must avoid using their unfamiliarity with a new technology to justify over-regulating a potentially beneficial advancement or employing what this article calls the “blockchain excuse” for regulation. On the other hand, antitrust enforcement must adapt to stay relevant, and this article suggests that regulators adopt a new methodology of “regulatory infiltration” using a “law is code” approach. Third, even if this new regulatory scheme is adopted, some ultimate questions demand resolution. This article seeks to address them in part three: is blockchain the death of antitrust law as we know it? Should it be? Answering those questions is not easy because blockchain continues to evolve. Nevertheless, the decentralized nature of blockchain forces us to consider the legitimacy of antitrust law, which rests on centralized legal structures and enforcement that are inconsistent with blockchain’s trustless nature; although, antitrust is still needed. This is the blockchain antitrust paradox.