You either get rules made up on the spot or selective enforcement / creative interpretation of rules.

Exactly... it's like everyone thinks they're a lawyer and want "clearly defined rules" until they get them and find there's gaping wide holes for interpretation, etc. Just like kids will push boundaries on literal interpretations. Then, as a parent, you clarify with "you know what I meant when X, right?" ... and then holding them to account all the same.

IMO, you're better off with expecting common decency and having leadership act as a judge when people act up. It's not "fair" but it's about as fair as reality is going to get. Most people are mostly good, and mostly reasonable. If you aren't rocking the boat, you aren't likely to have problems.