We, the Representative of the People of all that part of the Territory or country ceded under the name Louisiana, by the treaty made at Paris, on the 30th day of April 1803, between the United States and France . . . in Convention Assembled by virtue an act of Congress, entitled “an act to enable the people of the Territory of Orleans to form a constitution and State government and for the admission of said State into the Union on an equal footing with the original States, and for other purposes.” –Constitution or Form of Government of the
State of Louisiana,
1812
To what does the "treaty made at Paris" refer?

Which entity gives the territory the right to form a state?