Wiki:
The 1807 Act has been modified twice. In 1861, a new section was added allowing the federal government to use the National Guard and armed forces against the will of the state government in the case of “rebellion against the authority of the government of the United States,” in anticipation of continued unrest after the Civil War.[5] In 1871, the Third Enforcement Act revised this section (ยง 253) to protect Black Americans from attacks by the Ku Klux Klan.
Check the dates and make informed conclusions as to President and actions for and against the Union.
Soo... Grant? But the question was former president, or ex president... like after his/her term.