The 0.3% Threshold

The 0.3% figure is the Δ9 THC ceiling that separates federal hemp from federal marijuana, measured on a dry-weight basis. It was never a scientific potency judgment — it traces to a 1976 botany paper whose authors used it to distinguish plant types, not to define intoxication. Its narrowness is what created the THCA market: a flower can hold 20%+ THCA while its Δ9 sits under 0.3%. States that test for total THC close that reading; the federal ban effective November 12, 2026 closes it nationally. Know which rule your state uses — our legality pages track it.