Only if they live here in the us with us. If they live in say, Norway, it might be legal there just like its ok to buy a suppressor at the local hardware store in England.
I wish more politicians actually went to the range and listened to all the guns shooting and making so much noise and they might get the idea that it should be illegal to make that much noise like they do with cars. So they made that law that you must have a functional muffler (suppressor) that quiets the engine to a certain degree to avoid being a sonic menace.
Did you know that SKS's have what looks to be one of those things? It holds the safety lever (that gets in the way all the time)