THCa (tetrahydrocannabinolic acid) is a naturally occurring compound found in cannabis. Unlike its more well-known counterpart, THC, THCa is non-psychoactive in its raw form. It only becomes THC when it's heated (a process called decarboxylation). Because THCa doesn’t produce a “high” unless it undergoes this transformation, it remains legal under federal law as long as it comes from hemp plants containing less than 0.3% THC.