The Parliament of the United Kingdom passes the Misuse of Drugs Act 1971 banning the medicinal use of cannabis.

The Misuse of Drugs Act 1971 is an Act of the Parliament of the United Kingdom. It represents action in line with treaty commitments under the Single Convention on Narcotic Drugs, the Convention on Psychotropic Substances, and the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances.Offences under the Act include:

Possession of a controlled drug unlawfully

Possession of a controlled drug with intent to supply it

Supplying or offering to supply a controlled drug (even where no charge is made for the drug)

Allowing premises you occupy or manage to be used unlawfully for the purpose of producing or supplying controlled drugsIt is often presented as little more than a list of prohibited drugs and of penalties linked to their possession and supply. In practice, however, the act establishes the Home Secretary as a key player in a drug licensing system. Therefore, for example, various opiates are available legally as prescription-only medicines, and cannabis (hemp) may be grown under licence for 'industrial purposes'. The Misuse of Drugs Regulations 2001, created under the 1971 Act, are about licensing of production, possession and supply of substances classified under the act.

The act creates three classes of controlled substances, A, B, and C, and ranges of penalties for illegal or unlicensed possession and possession with intent to supply are graded differently within each class. The lists of substances within each class can be amended by order, so the Home Secretary can list new drugs and upgrade, downgrade or delist previously controlled drugs with less of the bureaucracy and delay associated with passing an act through both Houses of Parliament.

Critics of the Act such as David Nutt say that its classification is not based on how harmful or addictive the substances are, and that it is unscientific to omit substances like tobacco and alcohol.

The Parliament of the United Kingdom is the supreme legislative body of the United Kingdom, the Crown dependencies and the British overseas territories. It alone possesses legislative supremacy and thereby ultimate power over all other political bodies in the UK and the overseas territories. Parliament is bicameral but has three parts, consisting of the sovereign (Crown-in-Parliament), the House of Lords, and the House of Commons (the primary chamber). Both houses of Parliament meet in separate chambers at the Palace of Westminster in the City of Westminster, one of the inner boroughs of the capital city, London.

The House of Lords includes two different types of members: the Lords Spiritual, consisting of the most senior bishops of the Church of England; and the Lords Temporal, consisting mainly of life peers, appointed by the sovereign, and of 92 hereditary peers, sitting either by virtue of holding a royal office, or by being elected by their fellow hereditary peers. Prior to the opening of the Supreme Court in October 2009, the House of Lords also performed a judicial role through the Law Lords.

The House of Commons is an elected chamber with elections to 650 single-member constituencies held at least every five years under the first-past-the-post system. By constitutional convention, all government ministers, including prime minister, are members of the House of Commons or, less commonly, the House of Lords and are thereby accountable to the respective branches of the legislature. Most cabinet ministers are from the Commons, whilst junior ministers can be from either house.

With the global expansion of the British Empire, the UK Parliament has shaped the political systems of many countries as ex-colonies and so it has been called the "Mother of Parliaments".In theory, the UK's supreme legislative power is officially vested in the Crown-in-Parliament. However, the Crown normally acts on the advice of the prime minister, and the powers of the House of Lords are limited to only delaying legislation; thus power is de facto vested in the House of Commons.