It's a situation none of us even like to think about -- a violation of hunting laws and legal prosecution that follows. The harm to reputation of the hunter, the guide, the outfitter and the outside world's view of hunting in general can be enormous and irrepairable. Not to mention the great expense of the defense against such charges.
The bottom line in nearly every case is that it's up to the hunter to know the game laws -- ALL the game laws -- that could pertain to any given hunt in which he or she is participating. This does not mean "what the outfitter told me" either. It means, at the very least, a thorough reading of the published hunting regulations for the jurisdiction in which you are hunting -- whether or not your accompanied by a guide or outfitter. Additional research is wise prevention, too, as not all the laws are published in that flyer you get when you buy your license!
If there is a violation suspected, you as the hunting license holder (or should-be hunting license holder) will be held responsible. This covers violations of game and hunting regulations like being properly licensed for the area in which you are hunting and all of those other regulations governing the hunt whether you were outfitted or not.
If the alleged act is in violation of outfitting laws for that jurisdiction, then the outfitter is responsible and you would likely be considered a "victim" of the crime unless you knew of his/her illegal actions and enabled it.
It's all very messy, and something we don't wish on anyone. In part, that's why outfittersrating.com exists in the first place -- to aid you in finding legally operating outfitters of high integrity who follow the law and live up to their promises.
Again, the bottomline is that YOU need to know and follow the hunting laws for the area and season in which you are hunting as you will be held independently responsible for doing so.