The ABA has stringent standards for accreditation that include levels of tenured faculty and quality of library. This places an artificial floor on faculty wages and conditions that mean the adjunctification of university isn't going to happen to law schools.
And most newly minted law professors have real research doctorates in addition to J.D.s or top tire law degrees or both. They have much better outside academia options than social science or arts academics and their salaries reflect that.
No. Not at any reputable school. Getting a job as a law prof usually requires a degree above the normal law degree. And you better have gone to a top-tier law school. It's a real commitment.
While some US law schools offer what are termed masters (LLM) and doctoral (often 'SJD' or 'JSD' or the like) advanced degrees in law, few law professors (other than those with a first law degree from outside the US) have such degrees. (Edit: It's somewhat more common to see law professors with a JD and a PhD in some other field such as economics or history, but this is still not the typical profile of a law professor at any tier of US law school.)
At least at the relatively elite law schools, law professors do tend to be hired not too many years out of law school, often following a prestigious federal judicial clerkship and perhaps a couple of years of a stint at a top law firm. (That's probably mostly because those are the relevant biographical characteristics of those doing the hiring.) It is relatively uncommon to hire very experienced professionals (apart from adjunct positions). As you move to less elite tiers of law schools you see more ordinary faculty drawn from experienced professionals not necessarily having the cookie-cutter star credentials new hires at the elite schools have.
First year classes may be taught by either very experienced law professors or fairly junior ones.
I wonder if there are any stats on the wages of law professors? Seems they would trend down? Do recent grads teach first year law classes?