How did Thomas Jefferson justify the Louisiana Purchase?
He justified the purchase by using the presidential authority to make treaties.
He argued land purchases from foreign powers were legally similar to treaties and therefore constitutional.
Since it was not directly written on the constitution about buying or obtaining new lands, by purchasing the Louisiana Purchase, Thomas Jefferson used the idea of the elastic clause and the necessary and proper clause to justify his actions. Thomas Jefferson also stated that since it was the president's power to make treaties it is implied to obtain new lands