I called around to a couple of national environmental organizations(NRDC, Greenpeace and Sierra Club) and asked them. The consensus seemed to be go to the best law school you can and network in the environmental community like mad. I think the advantage to a school with a strong program is that the networking might be easier. The competition in the field is insane so, being able create personal contacts seems to be key as well as excellent grades. I have a UG in enviro studies so I opted for the higher ranked law school(and the scholarship money), but if my UG was in say history or PoliSci I might have I chosen Pace.
Thats my two cents.