in the united kingdom, certain drugs are classified as controlled drugs. controlled drugs are illegal to possess, use, or supply to others without a license. these drugs are governed under the misuse of drugs act of 1971. this act defines three categories of controlled drugs: a, b, and c. the penalties for illegaly possessing, using or supplying a controlled drug are different depending on which category the drug belongs to. many of these drugs are also governed by other laws, such as the medicines act. also, there are many other drugs that are not controlled by the misuse of drugs act but that are controlled by other laws.