I honestly have no clue about the actual legality, but the fact we have wild specimens that are commonly called "Chinese Mantids" probably answers it.
I don't know why they would be illegal, they don't do anything besides eat bad insects and are thus beneficial. But then again, our government does make up the damnedest rules without thinking it through sometimes.
The USDA considers anything that eats plants OR eats plant pollinators to be potential pests. They claim that it is mites that may come in on imported mantids that they are worried about. They've siezed mantids in import shipments, wholesalers and at reptile shows. They haven't indicated what, if anything, they intend to do about private hobbyists that have them.
The Chinese mantid is well established in the US and locally collected specimens are not considered exotic by the USDA.
So does that mean orchid mantids are illegal too? Or is it an area thing as tropical mantids cannot survive our winters. I have seen serval differnt species for sale at some petshops up here and they were not the Chinese mantids either, they were from Africa.
The way the regs are written, all exotics are illegal, regardless of their ability to survive. However, there doesn't seem to be much, if any, enforcement on exotic mantids being reared domestcally. I don't know if there's been an offical policy change to allow them (I doubt it) or if their main concern is blocking imports.