Cannabidiol and all other plant cannabinoids are Schedule I drugs in the US (per code 7372). So, technically, CBD is forbidden in any form (as an isolate or plant-based derivitive) in the states despite its lack of addictive potential and strong safety profile. In other words, although CBD is not psychoactive, it is still illegal in the eyes of the federal government. That said, there are exceptions. American scientists with a DEA license in some cases are permitted to experiment with pure synthetic CBD.
Some online businesses falsely claim that CBD oil derived from industrial hemp grown abroad is legal in all 50 U.S. states, as long as the THC content of this oil is less than .3 percent (in accordance with federal rules regarding industrial hemp products). Currently, it’s against federal law to use hemp leaves and flowers to make drug products. Hemp oil entrepreneurs attempt to sidestep this legal hurdle by claiming they extract CBD only from hemp stalk before importing it to the United States, a grey area activity at best. Although the FDA has issued warning letters against some CBD hemp oil companies for making false claims about their products, thus far the federal government has not take action to halt these illegal business operations. The situation is different in Europe, where CBD is not a controlled substance.
See Sourcing CBD: Marijuana, Industrial Hemp & the Vagaries of Federal Law for more information.