Max, I’m about midway between Beadalin (thanks for the vote of confidence, by the way) and TroubleAgain. It sounds a little fishy, but based solely on this description, it’s hard to draw any firm conclusions.
It’s correct that the interview questions should be limited to job performance, work history, skills, and so on. It’s within the realm of possibility that hobbies can come into it as well, though; I once got a job because of all the equally qualified candidates, I was the biggest movie fan, and therefore connected personally with the company president. That’s kind of a gray area, but generally it’s okay. However, religion, age, etc., those are all definitely out of bounds.
In my experience in HR, if we had a manager or interviewer who was asking those types of questions, we would unhesitatingly ask them to stop. Not necessarily because they’re clearly illegal, but because we don’t want anyone even to get the vaguest hint of a nebulous notion that we might have something potentially nefarious even flickering in the back of someone’s mind; we want to stay far, far in the clear. The questions as you’ve described them tiptoe up to the line, and whether they step over is entirely a matter of interpretation.
The easy answer is to suggest you wait and see whether or not you get the job. If you do, then you could call it moot and let it be. If you don’t, then you might want to investigate further.
However, even that makes my skin prickle a bit. A rigorously honorable person wouldn’t be able to leave a questionable situation alone, even if it happened to benefit them. How uncomfortable does it make you to think that this law firm might be qualifying people on religious grounds? If they offer you the job, can you honestly do it without wondering what was going on?
So here’s another question: You say you know your interviewers, and you went to school with them. Is there any possibility you could just ask them? Say, call them up and ask, unofficially, “What was that all about?” You could say you’re working on honing your interviewing skills, and you keep a journal or make notes or whatever afterward so you can evaluate your performance and continue to improve. “I’ve never been asked anything like that,” you could say. “Can you tell me what kind of information that was intended to extract?”
Obviously, the best solution would have been to say, “Why do you ask?” right there in the interview, but of course it’s too late now. Second-best, in the circumstances and in my opinion, is to call one of the interviewers and ask what they were doing. (Important: Do it in a casual, non-threatening, non-leading way, without giving any indication that your subtext is, “Were you asking about my religion?”)
Third-best, again in my opinion, is to wait to see whether you got the job or not, and then decide what to do from there: Either you get the position, and you must explore your conscience, or you don’t, and you must consult an attorney.
Oh, and one last thing, Max: Write down what happened in the interview, right now, all the questions and answers, while it’s still fresh in your mind. These things fade quickly, so make notes immediately, while you still can. Include everything you remember, not just the questions that bothered you, so everything is in context. If it comes down to making an accusation, you have to be scrupulously fair from your side as well.
And please, keep us posted.