What does Jefferson say about whether the US Constitution allows for an agreement such as the Louisiana Purchase? How can you tell?

The Louisiana Purchase was very controversial at the time. President Jefferson believed in a strict construction of the US Constitution — unless the Constitution specifically granted a power to the government, the power belonged to the people. Nearly doubled the size,allowed Americans control of the Mississippi,and allowed Americans to have western expansion. How did the president violate the constitution by making the Louisiana purchase? Because it didn't say anywhere in the constitution that the president could buy or sell land.