I'm not thinking of this politically, but more that it seemed like Micah was looking towards the Paladin Oaths as an inspiration. Which, in theory, is DnD's most famous attempt at this sort of binding promise type of mechanic, where if you violate the oath, you lose your powers.
But, while Paladin oaths kind of work... a Pact of the Fiend oath wouldn't. It couldn't. Not because players won't accept it or anything, but an Oath to Fierna is going to be different than an Oath to Mammon is going to be different than an Oath to Orcus is going to be different than an Oath to Graz'zt. Now, we did get Demon and Devil Cults in Mordenkainens' Tome, so maybe you could use that... but then you still haven't covered the Pit Fiend #3 or Erinyes #245 who could also be pact bearers.
And this is JUST the Fiend Pact, and WITHOUT getting into multiple settings. You would then need to do the same process for GOO, Fey, Celestial, Genie, Undying... you start getting to the point where having these sets of rules and pacts created and put into the rulebooks stretches out to be nearly a book on its own. And all designed with the sole purpose of removing a warlock's powers if they break one of these rules? It doesn't work.
Now, that isn't to say you can't have a far more generic system, like the piety or honor systems that do already exist. But since those are optional, and the details of the deal and restrictions would still need to be discussed with the player... we are back to where Micah doesn't want to be. Relying on the Player to come up with restrictions, instead of them being enforced by the system.
