Charlie,
Thats sad mate, in the UKwe have strict laws regards producing fake Patented stamps, and those laws I would assume would apply there in the States to, if it was a UK manufacturerss stamp being copied.
Is it allowed in some States or this just a plain rip off and copy of an original stamp and passing them off as original, because that, is a whole new ball game and here in the UK would be dealt with as Deception by the Police, big big fine and then the company would probably jump on you from agreat height!!
Thats how I would play it as an ex Police Officer, quite serious "with intent to deceive" all day long!
Incidently, there is also an offence for "knowingly" buying a counterfeit in this particular case too.