In the United Kingdom Cannabis was downgraded in 2004 from a Class B to a Class C drug, with lower penalties for possession and use. However then in 2009, against the advice of the governments own commissioned report, reclassified Cannabis back to a Class B. Later that year the chairman of the governments Advisory Council on the Misuse of Drugs, Professor David Nutt, was asked to resign from his position by the Home Secretary after putting forward the opinion that cannabis was less harmful than both alcohol and tobacco. Several other members of the Advisory Council resigned in protest.

Under the Misuse of Drugs Act, Cannabis as a Class B drug is illegal to possess, grow, distribute or sell in the UK without a license from the Home Secretary. The Home Secretary does not issue licenses, effectively making Cannabis completely illegal. Possession will generally result in a confiscation and a warning for small amounts. Mostly police forces operate along guidelines that if someone has been caught before within a 12 month period then they are arrested if caught again. However this can lead to up to 5 years in prison if deemed a serious offense. The cultivation, sale and trafficking are punished by up to 14 years in prison, an unlimited fine or both.