Digital constitutionalism emerges as a new ideological movement aiming to translate the values and principles of contemporary constitutionalism into the changed context of the digital society. This approach informs an ongoing process of constitutionalisation, which currently affects not only the state dimension, but operates simultaneously at several levels, including the regulatory sphere of online platforms, the so-called lex digitalis. The paper examines this cross-fertilization between state and private constitutional levels, exploring in particular how the principle of the rule of law, a value that emerged in state constitutionalism, if properly translated, can help guide the process of constitutionalisation of the lex digitalis.