The concept of the medieval lex mercatoria is experiencing a renaissance in the context of the global spread of information and communication technologies and the scaling of cyberspace. Globalization was replaced by networkization, which gave rise to the phenomena of networks, network communities, network communications, and network law. The author has chosen an appropriate research angle — a look at the lex mercatoria through the prism of the current network world order. This led to the conceptualization of lex communitas as «community law», which is the main object of the study. Lex communitas is considered as a modern historical form of lex mercatoria, mediating the non-state rule-making of international professional communities, the multiplying functional subsystems of which include lex informatica, lex sportiva, lex constructionis, lex petrolea, lex proprietas intellectualis, lex cryptographia, sustainable business law (sustainable business law), etc. Affiliation with one or another professional community is the basis for the application of the norms of lex communitas. This approach, in a sense, opens up prospects for posing the problem of the grounds for legitimacy, of ways to legitimize the norms of non-state regulation in the subject area of private international law. The concept of lex communitas correlates with how the modern system of resolving cross-border private law disputes is being transformed, increasingly moving to an extrajudicial plane: from international commercial arbitration to platform and decentralized systems. The paper attempts to identify certain features of the current stage of development of the lex mercatoria, the quantitative composition of the norms of which is rapidly multiplying in parallel with the ongoing qualitative changes in the system of regulation of cross-border private law relations.