Law may be an "iffy" subject, especially if it's one of your three full A-levels.
Although Oxford refuse to issue a black-list like Cambridge and LSE, it may be harder for you to compete as you have Law and AS Product Design. They're not "traditional" subjects, and there will probably be others applying for PPE who will have 3 or 4 A-levels in traditionally academic subjects.
But, to answer your question, yes, 3 full A2's is enough to apply and be accepted into Oxford. The subjects of those 3 A2's matter though.
Don't get me wrong, I'm not saying you don't have chance! The only people who can tell you honestly are the admissions tutors, but as far as people with offers for Oxford go, they tend not to have subjects like Law included in their offers.