At PPL, CPL & ATPL levels I just read & re-read the regs, orders, AIP & ERS/ERSA with the published syllabus next to me. Shock....horror but back then the law exams were in two parts with open & closed book sections and a pass required in both sections. *NO* tagging, marking or highlighting was allowed.
None of the air law exams are that hard. Read. And re-read. Then do it again. CASA's goal is for you to be thoroughly familiar the the rules and where they're located.