Civil rights activists challenged Southern voting laws because they conflicted with

a. the Fifteenth Amendment.

b. the Civil Rights Act of 1964.

c. the Emancipation Proclamation.

d. the Declaration of Independence

It was the Fifteenth Amendment. It gave all men in America the right to vote. South though opposed this and made many attempts to prevent Blacks from voting. It Federal intervention as the National Guard had to escort African Americans to vote in the polls.