Cannabis and international law

Cannabis reform at the international level refers to efforts to ease restrictions on cannabis use under international treaties. Internationally, the drug is in Schedule IV, the most restrictive category, of the Single Convention on Narcotic Drugs. As of January 1, 2005, 180 nations belonged to the Single Convention on Narcotic Drugs.
The Single Convention on Narcotic Drugs makes a distinction between recreational, medical and scientific uses of drugs; nations are allowed to permit medical use of drugs, but recreational use is prohibited by Article 4:
The Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances requires its Parties to establish criminal penalties for possession of drugs prohibited under the Single Convention for recreational use. A nation wanting to legalize marijuana would have to withdraw from the treaties; every signatory has a right to do this.
As of January 2009, "cannabis, cannabis resin, cannabinol and its derivatives" are categorized as Class B drugs, in accordance with "(Amendment) Order 2008" of the United Kingdom's Misuse of Drugs Act 1971. Following a proposal by UK politician David Blunkett "to seek the reclassification of cannabis from a Class B drug to a Class C drug" in 2001, the classification was moved to the less stringent Class C in January 2004, but was returned to Class B in January 2009.
The issue has become more pronounced with the legalization of recreational cannabis in Uruguay in 2013 and Canada in 2018. As of 2020, both countries are in direct violation of the Single Convention on Narcotic Drugs due to their legalization of commercial cannabis sale and production.
Barriers.
Some barriers to cannabis reform are the result of the international drug control structure, while others are related to political circumstances. A number of non-government organizations support the prohibition of cannabis as a recreational drug. In 2013, 97 NGOs in 37 countries joined the World Federation Against Drugs.
Bureaucratic.
The international drug control system is overseen by the United Nations General Assembly and UN Economic and Social Council. The Single Convention grants the Commission on Narcotic Drugs the power to reschedule controlled substances. Cindy Fazey, the former Chief of Demand Reduction for the United Nations Drug Control Programme, said:
To modify cannabis regulations at the international level, a conference to adopt amendments in accordance with Article 47 of the Single Convention would be needed. This has been done once, with the 1972 Protocol Amending the Single Convention on Narcotic Drugs; as Fazey notes, this process is fraught with bureaucratic obstacles.
Political.
In reference to situations where the Commission on Narcotic Drugs proposes changing the scheduling of any drug, "(d)(2)(B)" of The U.S. Controlled Substances Act gives the Secretary of Health and Human Services the power to issue recommendations that are binding on the U.S. representative in international discussions and negotiations:
The U.S Department of Justice Drug Enforcement Administration (DEA) denied in June 2011 a petition that proposed rescheduling of cannabis and enclosed a long explanation for the denial.
On March 5, 2013, the International Narcotics Control Board (INCB) urged the United States government to challenge the legalization of marijuana for recreational use in Colorado and Washington. INCB President, Raymond Yans stated that these state laws violate international drug treaties, namely the United Nations Single Convention on Narcotic Drugs of 1961. The Office of the US Attorney General said in December 2012 that regardless of any changes in state law, growing, selling or possessing any amount of marijuana remained illegal under federal law. Raymond Yans called the statement "good but insufficient" and said he hoped that the issue would soon be addressed by the US Government in line with the international drug control treaties.