Synthetic cannabis
It has also been difficult for states and countries to make synthetic cannabis illegal because there are so many different cannabinoids.  For example, in 2009, the United Kingdom made all the cannabinoids that existed illegal.  However, scientists quickly created new versions of cannabinoids, which were not listed as illegal in the U.K.'s laws.  Like many other countries, the United Kingdom has tried to ban every new cannabinoid as soon as it is created, but new ones are made all the time.