The rule of law establishes, first of all, that the Law does not distinguish any kind of person from another. This is why in order to have a true Rule of Law, the three powers (Legislative, Executive, and Judiciary) must be truly separated.
Decrees are exactly one way to subvert it: the executive acts as the legislative.
Also, in tyrannies (vid. Venezuela, Iran, etc.), the Judiciary is a slave to the executive.
The rule of law states, first of all, that people in Government are subject to the same laws as any other citizen.
It is obviously an unreachable optimum (like true "democracy" is), but that is the basic principle. Not that "Laws" govern the place.
Chat Control (and see especially the Danish Minister who said "common citizens should not expect to be able to use cryptography" or words to that effect) is suspicious under the rule of law because it differentiates ipso iure between "ordinary citizens" and "the executive".
Edit: whether you agree with him or not, reading "The road to serfdom" should enlighten you a lot about this topic.