Well, we have specific rules that restrict something like this. If you see someone nonsec validhunting, you should report them to admins. And ofc there are certain valid antags (wizard, nukies, blob, demons) which are perfectly valid to be hunted by anyone, and i dont see any problems for miners to use gear from lavaland to do it effectively. Not like killing megafauna is easy enough for miners to storm maintenance in full gear 10 minutes into the round.
Also restricting antags from using lavaland loot is also a bad descision. All the fun around lavaland is to bring loot to station. Also often miners share gear with sec or command.