More often than not, stores sell whatever stock they have at the time the ban is effected. From my personal experience, third party retail stores such as Best Buy are more likely to do this than carrier locations such your local mall's Verizon Wireless.
Additionally, some such bans specify what should be done with un-sold stock. In some cases, in-store sales are supposed to stop, while other times, shipments to all retailers are simply halted. The decision is affected largely by the judge's belief that the winning party could suffer damages by any further sales.