There is a lot of confusion in the United States regarding cannabidiol (CBD). CBD from hemp is federally legal as long as it contains no more than .3% THC.
But some states have put restrictions on buyers. Hemp, according to law, is defined as cannabis with very low tetrahydrocannabinol (THC), which is the molecule that can cause a high when heated. On the contrary, CBD derived from cannabis with high levels of THC is illegal in many states.
The confusion also stems from restrictions in farming. Unlike corn, wheat and other natural products, hemp has not been as easily farmed. However that is getting ready to change due to the passing of the 2018 Farm Bill. Until 2014, in the United States, the only legal hemp was imported mostly from Europe, China and Canada.
For more information see Is CBD Oil Legal