Depends which country in Europe you are talking about. No handguns (of any kind) plus no semiauto rifles and shotguns in Britain, no "military calibers" (9mm, .223) to civilians in some countries like France, no "military looking" guns in Germany. On the contrary to that about all allowed in Switzerland.
Here in Finland every gun (except air guns) need a permit, but all kinds of guns are legal without mag cap (except for hunting), pistol grip etc. restrictions, and mail order sales of guns are legal (and common), as are silencers also. Full-auto models are only for accepted gun collectors. Big differences between different European countries, but in the USA there is also a big variation between Texas and California, I have heard.
Ossi