If it's in some place like NJ, an FFL is still required AFAIK. The State law does not ackn the Fed Antique Status there (nor C&R). Other States have similar laws. NY does not ackn Antique Status of a cartridge handgun (one very grey area about obsolete chamberings aside).
But you're most probably up against an FFL that wants to dazzle the compliance agents with paperwork when they come knocking.
As already stated, you probably can't convince him otherwise.
Most FFL's are in extreme CYA mode as of the last few years.
Their call, their license.
I've always figured just following the printed rules was a good tactic.
