Law 53 of 1948 (Gag Law / Ley de la Mordaza)

Law 53 of 1948, known as the Ley de la Mordaza (Gag Law), was enacted by the Puerto Rican legislature on June 10, 1948. Modeled after the U.S. Smith Act of 1940, it made it a crime to own or display a Puerto Rican flag, to sing a patriotic song, to talk of independence, or to meet with anyone to discuss Puerto Rican independence.

Specifically, the law made it illegal to:
- Own or display a Puerto Rican flag
- Sing patriotic songs
- Talk about independence publicly
- Meet with anyone to discuss independence
- Print, publish, sell, or exhibit any material promoting independence

Violators could be sentenced to up to 10 years in prison and fined up to $10,000. The law was used to arrest and imprison thousands of independence supporters, including members of the Nationalist Party, labor organizers, and intellectuals.

The law was championed by Governor Luis Muñoz Marín, who had shifted from supporting independence to advocating commonwealth status. It remained in effect until 1957, when it was repealed after years of criticism. The Gag Law is considered one of the most severe restrictions on civil liberties in the history of any U.S. territory.