Who gives the federal government athourity to negotiate trietes with forigeon nations?

The authority for the federal government to negotiate treaties with foreign nations is derived from the U.S. Constitution, specifically Article II, Section 2. This section grants the President the power to make treaties, provided two-thirds of the Senate concurs. Additionally, the Supremacy Clause in Article VI establishes that treaties made under the authority of the United States are the supreme law of the land.