It is often not possible or desirable to have laws that are so complete and exhaustive that they require 0 interpretation. Laws, like most thing, are designed to try to balance flexibility and clarity where necessary. Otherwise, they are mostly worthless, or become worthless very quickly. (and no, you can't just make them super explicit and constantly update them, it's completely intractable)

As a result, pieces of government offering guidance/manuals for their enforcement is very common.

This is true both criminally and civilly.

For example, the USPTO maintains the "manual of patent examining procedure" that somewhat exhaustively interprets patent law.