602.1.h.2. Players may select any battlefield from their sealed card pool during game start procedure.
602.1.h.2.a. In events where sealed deck registration is required, players must register a battlefield to be used in the first game of a match.
602.1.h.2.b. Players may only use a specific battlefield once per match, but may use the same named battlefield as many times as they have copies of it in their sealed card pool.