Which event was most responsible for Richard Nixon announcement of the end of the Indian termination policy?

The Native Americans' peaceful. 19-month occupation of Alcatraz Island.

Belvin realized that, over time, the bill cut the tribe's access to public loans and other services, including the exemption from tribal taxes. By 1967, Oklahoma Congressman Ed Edmondson had been asked to attempt to abrogate the termination act. On 24 August 1970, Congress finally repealed the law.