You watch too many movies and are losing your mind!

The first thing about artificial intelligence is that it will be intelligent.

Thus, if it was used as law enforcement, it would immediately shut down because our legal code is too big and often self-contradictory. An intelligence smart enough to work with all of the codes and laws, would be smart enough to know that it couldn't apply them. So it would sit there until law makers fixed the codes and laws.

Again, after that the AI would see what it was doing, and see the outcomes. The outcomes are what the AI uses to teach its flow control (to learn) to apply to new inputs. Thus it would quickly come to the conclusion that incarceration is a poor punishment.

So, the bad, over enforcing, cruel, inhumane "AI" would actually have to be a program that was designed to not be self learning, but just a thing that ran around spatting "code violation" and punishing random people for random things. Not at all intelligent.

And if there was some machine so blatant then people would put a stop to it. There would be no concern like you would have for a living police officer. And there is so many ways to stop a machine. Anything that breaks anything in the complex manufacture, repair , supply chain stops a machine.

Further, defense robots are FAR cheaper and easier to make.
You will see in the near future, the response to drones will be flying bricks.
A million dollar machine reduced to a splat on the ground by a $10 drone who's whole program is just to get in the way.

Today's movies are very much designed to make you feel ineffectual and ineffective.
Thus the idea of T.H.E.M. using an "AI" to enforce law seems scary.
But really, it leads to all kinds of good results.