The short answer
THCA is tetrahydrocannabinolic acid, and a cannabis plant makes it while it grows. Heat turns THCA into delta-9 tetrahydrocannabinol, or delta-9 THC. Whether you may buy a THCA product depends on your state, and on which federal definition of hemp applies on the day you buy it. The definition in force now measures hemp by its delta-9 THC concentration, at not more than 0.3 percent on a dry weight basis (7 U.S.C. § 1639o. Definitions (as amended by Pub. L. 119-37 § 781, whose scope is limited until 2026-12-11 by the Continuing Appropriations and Extensions Act, 2027, § 2019)). A replacement definition changes what counts toward that 0.3 percent, and it reaches flower from December 11, 2026 (Pub. L. 119-103, § 2019, Section 781 Extension (Continuing Appropriations and Extensions Act, 2027; enacted 2026-09-02, linked text as enrolled because the slip law is not yet published)).
The detail
The two molecules differ by a carboxyl group, and THCA is the one that carries it. Heat removes that group as carbon dioxide. Time and warmth remove it more slowly.
THCA flower is cannabis flower that has not been heated. A grower cuts and dries it like any other cannabis flower. Most of what it holds is still the acid rather than delta-9 THC. Shops sell it as a hemp product on the delta-9 measure.
Section 781 of Public Law 119-37 strikes the paragraph that holds the current definition and inserts three paragraphs in its place. The first limits hemp to 0.3 percent total tetrahydrocannabinols, counting tetrahydrocannabinolic acid, so flower over that figure is not hemp (Public Law 119-37, div. B, title VII, § 781, Nov. 12, 2025, 139 Stat. 558 (scope limited until 2026-12-11 by the Continuing Appropriations and Extensions Act, 2027, § 2019)). It takes effect on November 12, 2026, which is 365 days after the Act was enacted.
Until December 11, 2026, only two of the new definition's categories apply, and both are written for cannabinoids a Cannabis sativa L. plant cannot naturally produce (Pub. L. 119-103, § 2019, Section 781 Extension (Continuing Appropriations and Extensions Act, 2027; enacted 2026-09-02, linked text as enrolled because the slip law is not yet published)). Flower that holds only what the plant made is in neither category. What does the December 2026 federal hemp rule change? sets out both dates and the rest of what the amendment does.
What varies by state
What a shop in your state may sell is a separate question from the federal measure. Each state's page has a section headed Hemp-derived products. Where this site could read the state's own rule, that section cites it; where it could not, the section says information is coming soon. Find your state on cannabis law, state by state.
In 5 states the only counter you can lawfully buy cannabis products from sells hemp-derived ones: Kansas, South Carolina, Tennessee, Wisconsin and Wyoming. Another 2 license no cannabis shop of any kind: Idaho and North Carolina. What either state permits without a license is on its own page.
This site lists a shop only where a state issued it a license. Where a state licenses the shops that sell hemp-derived products, and this site holds records for them, they appear under that state. A store page names the authority that issued the license, and the license number where the state publishes one.
What to watch out for
A certificate of analysis that gives a delta-9 THC figure on its own reports the figure the definition in force now uses (7 U.S.C. § 1639o. Definitions (as amended by Pub. L. 119-37 § 781, whose scope is limited until 2026-12-11 by the Continuing Appropriations and Extensions Act, 2027, § 2019)). It does not report the total the replacing definition uses. A total that counts the acid is never lower than the delta-9 THC figure by itself.
Do not read a low figure as a rule that THCA is never counted. A state or tribal plan must include a procedure for testing a hemp crop using post-decarboxylation or other similarly reliable methods (7 U.S.C. § 1639p(a)(2)(A)(ii). State and tribal plans: testing using post-decarboxylation or other similarly reliable methods), and so must the plan the Secretary runs where no state or tribal plan is approved (7 U.S.C. § 1639q(a)(2)(B). Department of Agriculture plan: testing using post-decarboxylation or other similarly reliable methods). The test accounts for the acid, either by converting it before the reading or by counting it into the total.
A state page's last-checked date says when a person read that state's rules against the sources named on it. It says nothing about the two federal dates above, which an Act of Congress sets.
Where to go next
What federal law says about weed sets out what the rest of federal law does about cannabis, with its own sources. Cannabis law, state by state is the index of the state and district pages.
Search the store directory by city or ZIP code. It holds a page for each licensed location this site has an active record for.