I know what Massive Scarlet coral is -- Siderastrea siderea, but don't know/can't find anything on 'scarlet coral.'
As far as I'm aware, elkhorn coral (Acropora palmata) and staghorn coral (Acropora cervicornis), are the only corals on the Endangered Species act. Even then, owning the coral would not be illegal, buying/selling it would be. Siderastrea siderea is protected in certain areas. If the coral was collected in non-protected waters, it should be fine. Or in your case, if the coral grew on live rock that was harvest, it's fine as well.