Flynn was a "a titan in the UK drug law reform movement" according to the Transform Drug Policy Foundation, a think tank of which he was a patron. This involved asking numerous oral and written parliamentary questions at the request of Transform, tabling early day motions and private members bills, hosting events in Parliament on behalf of the charity, as well as doggedly raising the issue of drug law reform in the house in a series of memorable barnstorming speeches. His speeches included objecting to the classification of psilocybe mushrooms as illegal in the Drugs Act of 2005, in which he said: "We cannot make nature illegal.
Flynn was a key figure in the UK's drug law reform movement, according to the Transform Drug Policy Foundation, which he supported as a patron. He actively engaged with the issue through parliamentary questions, motions, bills, events at Parliament, and impactful speeches advocating for change within the House of Commons.