The relevant law was posted. You just chose to ignore it because it doesn't support your position and we wouldn't rubber stamp your twisted interpretation. But I'll tell you what, kid.

You go talk to a lawyer. Any lawyer you like. Tell him that since the city law does not expressly prohibit locking your bike to a street sign, the university is therefore blocked from making such a prohibition themselves, and if they do, they have to email you with a notice of such.

Then come back and tell us how long it is before he stops laughing.