The December 11 rule counts total THC, including THCA, and caps THC at 0.4 mg...

https://stephensnewop-eds.quantlynix.com/posts/what-does-thc-free-actually-mean-for-cbd-isolate-suppliers

The December 11 rule counts total THC, including THCA, and caps THC at 0.4 mg per container. That narrows the market for intoxicating hemp products and shifts demand toward compliant, THC-free inputs backed by batch lab reports.