From Ilesol, “New Guidance on CBD in the UK”:
“According to the guidance from the Home Office, the products on the market that can be exempted from the ban of the controlled substances are those whose components don’t contain more than one milligram of a controlled substance. The threshold of one milligram made it possible for CBD manufacturers to demonstrate that their products don’t have an over-the-limit presence of psychoactive substances and, as such, are legal in the UK.
However the amount appeared straightforward, it seems to have presented difficulties in interpretation and analysis, as the Government Chemist team pointed out in their new publication.
They found it unclear whether the threshold of one milligram applies to each illicit cannabinoid or the total sum of them, so they decided to take a worst-case approach, and assumed that the 1 mg threshold covers all psychoactive cannabinoids.
To avoid costly analytical challenges, the list of twelve cannabinoids can be shortened to five that need to be taken into account for the analysis. Combined, they should efficiently represent the presence of psychoactive cannabinoids in a product. Those are Δ9-THC, Δ9-THCV, Δ8-THC, CBN, and cannabinol methyl ether-C5.”