@Oofta, it's obvious that this is a pretty touchy topic for you. It's also obvious that you haven't actually read the module and you are making decisions based on very limited information. Please, if you want to actually contribute, take the time to read the module instead of constantly having to be corrected because you haven't.
The following things are true:
1. No one has died.
2. Gingawazim are a small aberration. While it is true they could kill someone, that's true of lots of things. If I sell you a horse and that horse kills someone, am I culpable? Obviously not. So, comments about "loaded guns" and the like are not really applicable here.
3. The ONLY reason that this particular Gingawazim attacks the PC's is that it was ordered to stay in book form and was thus starving. Had it been allowed to hunt, it likely would have fed on stuff smaller than itself - ie. tiny stuff. Not many things normally try to eat stuff that's bigger than it is.
4. No laws were broken in Candlekeep save the entrance law. In fact, Candlekeep does not have any real legal system. Anyone who breaks rules is just banished from Candlekeep. Full stop. Kill someone in Candlekeep? They just push you out the door, never to return.
5. Baldur's Gate has been detailed in the Avernus adventure, which, I presume, includes Baldur's Gate's approach to legal issues. So, claims about canon not applying anymore are false.
6. AFAIK, no laws were broken in Baldur's Gate. Maybe, maybe, you might get a fraud charge to stick and that's it. If Baldur's Gate even HAS a fraud statute. No one was injured or harmed in Baldur's Gate. So, any legal issues won't be resolvable in Baldur's Gate. Nor, unless the DM grants it, does the party have any legal standing. Candlekeep simply wants the books back. Other than that, they don't really care. No one in Baldur's Gate would care, frankly, that non-citizens got fleeced at a market.
No matter what, nothing the Amberdune group have done would even remotely warrant a death sentence. In fact, if you set this in Waterdeep as
@jasper did, then the party would actually be arrested and executed for killing within the walls of Waterdeep. Waterdeep doesn't have any self-defense or whatever defense. You kill someone in Waterdeep, you are going to the salt mines if they don't flat out execute you. There's no extenuating circumstances allowed at all.