JHW-018 is a synthetic chemical with canabinoid-like properties. It is proven to be the active ingredient in spice and many spice alternatives by the German government, despite previous claims by the company that spice is all-natural. Theoretically, it is illegal to have in the United States. A large shipment of spice has been siezed by the United States government, although it was under the pretense that it contained HU-210 a different synthetic cannabinoid.
Realistically, it would be unlikely for any user to ever be prosecuted for possession of spice or related mixtures, although it is a legal hot-spot. Vendors are far more in danger than users.