The following are simply opinions (I am NOT a lawyer). First, I'm not sure if anyone can tell (based only on these photos) if anything pictured is "illegal" - for instance, any of the firearms depicted might actually be a non-firing replica. Second, the short barreled AR you mention has a buttstock, which I beleve makes it a rifle under federal laws/regs, rather than a pistol. Finally, state laws vary immensely, and other factors (the owner's legal status as a convicted felon or LEO, for example) might determine the legality of possessing anything shown in the photos...
In NYC all semiauto rifles are illegal - They have been so since the reign of king Dinkins. And yes the NYPD confiscated a number that were legally registered (in 1976 with the promise that the registration lists would never be used for confiscation)