Complex sentence: In the United Kingdom, MDMA is illegal under a 1977 modification to the Misuse of Drugs Act 1971 thereby making it illegal to sell, buy, or possess the drug without a licence.
Split into simpler sentences: In the United Kingdom, MDMA was made illegal in 1977 by a modification order to the existing Misuse of Drugs Act 1971. The drug is therefore illegal to sell, buy, or possess the drug without a licence.