IS THCA LEGAL?

The short answer is, “Yes”, under federal law. 
The idea that there are legal hemp buds that are no different from illegal marijuana buds seems counterintuitive, but proving that this is true involves a very straightforward analysis. The 2018 Farm Bill distinguishes legal hemp from illegal marijuana solely by reference to its D9 levels. Specifically, hemp is cannabis with no more than 0.3% D9 by dry weight. So, a hemp bud with THCa levels of 20% and D9 levels of 0.15% falls squarely within the 2018 Farm Bill’s definition of “hemp” and is legal under federal law.
In fact, the DEA specifically agrees that cannabis material meeting this definition is lawful. In a letter written on January 6, 2022, the DEA states: “material that is derived or extracted from the cannabis plant such as tissue culture and any other genetic material that has a delta-9 tetrahydrocannabinol concentration of no more than 0.3 percent on a dry weight basis meets the legal definition of “hemp” and is thus not controlled under the CSA.” This is not the first time the DEA has confirmed that the sole factor distinguishing lawful hemp from unlawful marijuana is its D9 concentration. In addition to confirming this standard in both a letter to the Alabama Board of Pharmacy and a public statement to the Florida Department of Agriculture and Consumer Services (both of which can be viewed by clicking here), the DEA’s Interim Final Rule regarding hemp states that marijuana is limited “to only include cannabis or cannabis-derived material that contain more than 0.3% delta-9-tetrahydrocannabinol (also known as D9 -THC) on a dry weight basis.”
In summary, harvested cannabis flower with D9 concentrations not exceeding 0.3% meets the legal definition of “hemp” and is not controlled under federal law, regardless of its THCa levels.