Is the ar15 in the 3rd pic in front of the ar15 with the bipod illegal? (Well I guess every gun is illegal in NY.) I thought they would have to be registered as a pistol? It is a very short barrel. Only some states or all?
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...
If it has a less than 16 inch bbl and a collapsible stock for a total fixed length of less than 26 inches, it would likely be a class 2 weapon, a short bbl’d rifle, SBR. If the stock is fixed at that short length, or is an arm brace type stock, it would be a pistol per ed law and most states. Probably all the above are illegal except for LE/govt types in NY, but all would be legal ( with a cl2 permit if an SBR) in my state, MO.