Electr[on]ic device regulations probably. There's always some form of a contract depending on the nature of a product/service. Enforceability is on parties to research.

I just sort of don't get the question here. Who's responsible? Well, there's no law of nature for that. You and your provider decide together, out of realistic reasons.

Who's stopping you? Probably some guys who got tired of figthing electric fires in their state/city. Maybe they'll consider regulating AI-related products as well, but if you're concerned then maybe you should think that through yourself and negotiate risks, before using/selling off the shelf AI.