There are two reasons to withdraw a law school application:
1. You were accepted and you know you do not want to attend; or
2. You were waitlisted and you know you do not want to attend.
In either case -although you’re not required- it’s nice to let the school know your intentions so they can move on to other prospective students. A simple one-sentence email to the admission office thanking them for their acceptance but politely declining is all you need to do.