Having played a provost or three, and one of the more lethal ones:

It was drilled into me by the immortals running the cabal, and something that I drilled into every single magistrate when interviewing them. The concept of Jurisdiction. The laws only apply within the jurisdiction you have. The example I typically used:

Scenario 1 - You are a magistrate of Galadon. You are protecting the Spire against a warranted outlander. They flee to Galadon and a healer there heals them. Can you warrant them?

Scenario 2 - Same as above, but they flee to the Weald. Can you warrant them?

The answers are Yes and No respectively. This is because in the first case you have jurisdiction, and in the second you do not. It is the same thing with a provost and his guards, or a vindicator and his guards. If either chases a criminal outside of a city using their guards, the criminal and his friends are allowed to strike the provost, the vindicator, the guards, or do whatever. It's not a protected area, so the laws of the spire do not apply. Basically, if you can't stand in the location and give them a warrant, then you don't have jurisdiction to enforce laws there.

The logical extension of your view is that once a character is warranted and retreats to their cabal, anyone who defends that cabal should then be warranted.

That, and having known your character through a few iterations, I think you should have ben OE, not ON. OE uses the laws for their own advantage.

Oh, and yes, all these provosts I mentioned are from within the past 20 years, so I don't know quite what you're talking about when you speak of this being the case for decades. This is a new development from my own experience through at least a half dozen magistrates in the past decade.