I always say university first to these questions. It is what I did, and it is also something that many of my friends (who started training straight from school) say that they regret having missed out on. However, it is very important that you enjoy the subject you are about to study, and also that it is the stepping stone to your second choice career if you do not make it as a pilot. So if you like the law, and would like to work in the law, I'd say go to university first.
After all, you can always keep your eye on the availability of flying sponsorships and scholarships, and quit the degree to start flying, if you are successful upon application for one.