Action Arms never imported any full autos.
Importation of transferable full autos ended in '68.
The D E S lowers have been available in parts kits here for years. Any work done to that gun was done in the states. There is no changing a full auto back to semi. If that gun was registered it can't be unregistered. If it wasn't registered before '86, modifying it so a open bolt will fit in the gun (or modifying the bolt) is illegal.