This puts a bit of a weird spin on it.
Especially after recent supreme court decisions, which I support, Congress has to give an agency specific authority within defined boundaries in order to make regulations which have the force of law.
Congress doesn't have to get down to the very specifics (like for example emissions standards numbers for cars), but it does have to be specific enough (can't say: EPA, you're responsible for environment stuff, make whatever laws you feel like).
For example the origination of the FTC https://en.wikipedia.org/wiki/Federal_Trade_Commission_Act_o...
The legislation charges the FTC with preventing unfair business practices, defines what it means by unfair, and then gives authority to address these things through administrative actions or the courts.