But that's not really how it works. I can buy things that are illegal here; but it's perfectly legal for the foreign company to produce, sell directly and post the product to me. It would be me that's committing the offence.
The FCC might have some chance if the company has a presence in the US; but -given their business- I wouldn't have thought so. There may be a few middlemen and importers the FCC could nail; but if producing jammers is legal in China then there's not a lot the FCC can do about it..