No it isn't. Guidance systems are perfectly legal. The FAA has some common sense restrictions like "you can't fly it at an airplane" or "you can't fly it over a crowd" or "you can't attach an explosive charge" but the only point to point flight profile that is illegal is that you can't launch into another country's territory. And of course these restrictions are on the flights themselves, not on the capabilities of the rocket.

Selling rocket guidance systems internationally is going to get you in trouble with ITAR, but that's a whole different can of worms.