Which amendment cut off US combat funding in Indochina after August 15, 1973?

The amendment that cut off U.S. funding for combat activities in Indochina after 15 August 1973 was the Case–Church Amendment.

Named for Republican Senator Clifford Case and Democratic Senator Frank Church, the measure was enacted in 1973 as Congress asserted greater control over the continuation of the Vietnam War. Its language barred funds from being used for direct or indirect U.S. combat activities in or over North Vietnam, South Vietnam, Laos and Cambodia.

President Richard Nixon signed the relevant legislation on 1 July 1973. The 15 August deadline ended the last ongoing American combat operations in Indochina, particularly the bombing campaign in Cambodia. The law did not immediately end all U.S. aid: military equipment and economic assistance continued to reach South Vietnam and Cambodia.

The name is often confused with the Cooper–Church Amendment, which earlier restricted U.S. operations in Cambodia. The Mansfield and Fulbright amendments were related congressional efforts, but they were not the canonical answer to this question.