Like the other poster said, you won't be choosing a major like you would in college, but you can get "certificates" in environmental or international law at Pace.
Certificates won't give you much of an edge in hiring and may only serve to narrow your opportunities after graduation. Environmental and international law jobs are rare specialties and graduating from Pace won't do you any favors. Generally, the only people who get these kinds of jobs are graduating from top-six schools. I'm not saying it's impossible, but it's extremely unlikely.
If you get a certificate in environmental law, employers in other areas of law may wonder if you're a flight risk. With the way the legal market is now, I'd want to keep my options open unless I were graduating from a top school, in which case I'd feel slightly more secure carving out a niche.
If you decide on tax law, then you'll really need to get an LLM in tax. I checked Pace's website and they do not offer a tax LLM, but that's probably a good thing. The best tax LLM programs are offered at NYU and Georgetown. (I'm going into tax law.)
As for the job prospects, they're not great. Pace is in New York and New York is a saturated legal market. Not only does NY have a large number of much better law schools all vying for jobs there, but every other law school in the country sends graduates there.
This is from a few years ago, when the market wasn't suffering so much. Even then, Pace wasn't doing very well. They weren't sending a lot of graduates to the top attorney jobs (blue) and the attrition rate (dropout / flunkout numbers) was quite high. Only 40?ere getting jobs in law firms at all, while the rest were unemployed, drop-outs or flunk-outs, working for some other type of business or going back to school to study something else. There were just a tiny handful who got some kind of prestigious clerkship. Imagine how bad it is now.
Unless you got a substantial scholarship, I can't imagine that this school is worth the investment. I wouldn't go here. I think I'd re-take the LSAT and re-apply. For the New York market, anything lower than Fordham is a big risk.
Good luck to you.