More bullshit from an disrespected agency.

They should have fought this.....the applicable language from the NFA is:

Suppressors - this includes any portable device designed to muffle or disguise the report of a portable firearm. This category does not include non-portable devices, such as sound traps used by gunsmiths in their shops which are large and usually bolted to the floor.

On the GSG-5SD it neither "muffles or disguises the report," nor was it designed to do so.

I cannot imagine what their reasoning behind this could be. If anything the part in question is a barrel shroud. It "looks" like a suppressor, that's all