What is the term for people get to vote whether or not they want to allow slavery in their territory?

The term is Popular sovereignty
This voting process was proposed by Senator Douglass in 1850 and regarded as one of the most controversial government decision in united states history.
the difference of decision between northern states and southern states regarding this matter eventually led to the American Civil War.

Opposition to the nra came to a head in 1935, when the conservative supreme court declared the agency unconstitutional, claiming the nra gave the executive branch regulatory powers that belonged exclusively to congress. this decision began a series of court decisions that overturned key elements of the new deal.