Is it worth applying to do Law with French with A*AB if it asks for AAA?

(Assuming you've obtained your A2 grades and will not be taking on any extra A-levels this year)

If the university does have any alternative offers, then no, the extra grade achieved in the A* will not compensate for the B. The AAA applies as a minimum across all three subjects. In fact, the only uni that I've seen offer an alternative offer for Law is Bristol, with its AAA [or] A*AB offers for the LLB.

If you're really committed to going to that university and course, I'd suggest taking out a year and re-applying, or taking an extra A-level and getting it predicted at A/A*. That will, however, make your offer conditional.

Ah, okay. Honestly, I wouldn't try to apply to too many AAA courses with A*A*B. If your own teachers don't believe that you're capable of getting that A/A* in your third subject, then why would admissions be any more lenient? I'm presuming that the admissions team know that, statistically speaking, most applicants don't actually go on to reach their predicted grades.

What universities are you thinking about?