We know AIs are easily transferable because when Momo and Marigold went to buy Momo a new chassis, Momo tried it on right there in the store with nothing but a thin cable connecting the two bodies.
There may very well be software and/or hardware protocols to
prevent AIs from being copied, however, if nothing else because of the legal complications that would arise if a sentient copy asserted its civil rights and demanded equal ownership of everything the original AI owned. Or worse, if the copy claimed that
it was the original and the other one was really a copy that had somehow switched bodies/hosts/chassises (what IS the plural of chassis, anyway?) with it, so it wanted full unshared ownership of everything the other AI owned. I mean, if the copy is completely identical, then how could a judge or jury tell which was the original?
It's the same basic problem that you have when live people can be copied, whether by some kind of fast cloning or because the Starship Enterprise had a transporter malfunction.
(Seriously, if a real-life matter transmitter had problems as frequently as the ones in Starfleet did, it would never have been approved to be used on ships -- at least not in a peacetime navy; these people didn't sign up to risk their lives just by routinely moving on and off the ship.)
Edit:
The PBS documentary "Neurotypical" included an autistic person who has a reputation as a wonderful conversationalist. He discovered that all you have to do is repeat the last few words the other person said.
"You just repeat the last few words the other person said?!"
Haha, that's brilliant!