The Chevron doctrine - https://en.wikipedia.org/wiki/Chevron_U.S.A.,_Inc._v._Natura....

This concept in the U.S. is also evolving since 2024 decision reducing the strength of this legal protection.

Practically all countries have some version of this, few hundred lawmakers and their staff cannot reasonably set every single policy and micromanage its execution for every for government function.

Civil servants always have a lot of say in direction of governance even if not directly enshrined in law or recognized by the court.

The classic 80s satire Yes, Minister is good illustration of the parliamentary version of how it happens in say England even if not enshrined in law so to speak.