Generally, a treaty is an agreement between nations. A treaty between the United States
and an indigenous Indian people is a contract between sovereigns. U.S. treaties are the
supreme law of the land.
U.S. Const., Art. VI, cl. 2. They carry the same legal weight as
federal statutes.  

It is generally the executive branch of the Federal Government – the branch led by the
President – that has the power to forge a treaty.  

Congress can repeal statutes. In like fashion, Congress can abolish treaties. Under U.S.
law, Congress does not require the consent of the other side to do this. If the United States
enters into a treaty with Russia, for example, or Iran, and then Congress passes a statute
that is inconsistent with the treaty, Congress’s statute controls. In that case, the agreement
set forth in the treaty no longer applies.  

Congress can state its intent to terminate a treaty agreement expressly. In that event the
United States no longer honors the treaty.

More commonly, Congress will pass a law in the ordinary course of its business that
happens to conflict, or appears as if it may conflict, with a treaty. In such situations, U.S.
courts must often decide what Congress really intended to do about the treaty when it
passed the law.  

If the court decides Congress intended to destroy the treaty agreement, then the United
States will no longer honor it. If the court decides that it did not so intend, often the court
will try to save the treaty agreement, or as much of it as it can, in rendering its opinion to
clarify what it thinks Congress meant to do.

In 1850, the year when California became a state of the United States, the U.S. President
appointed three commissioners to negotiate treaties with California Indians. The
commissioners' negotiations took place between 1851 and 1852. The commissioners
met with over 400 local leaders in the state and entered into eighteen treaties.  

The treaties accorded the Indian signatories 7.5 million acres of land, or about 8% of the
state, for their sole use. Much of it was quite good land for farming and mining. The treaties
also provided for clothing, food, livestock, farming implements, and educational services
to the Indian signatories in return for cession of the rest of the state.  

For a treaty to be effective under U.S. law, though, two-thirds of the U.S. Senate must
approve it. When these 18 treaties from California came before the U.S. Senate, miners
and settlers in California advocated against approval. Anti-Indian sentiment in California’s
new state Legislature was running very high. Its members strongly opposed federal
confirmation and pushed for the Federal Government to actually force all of the California
Indians out of the state.

The United States Senate bowed to some of this pressure from California and, in a secret
vote which remained classified for five decades afterward, declined to approve the
negotiated treaties. So the 18 treaties never became effective. This caused the Indian
signatories considerable frustration. Many Indian people in California are still frustrated
about Congress's failure to approve these treaties. The three commissioners who
negotiated the treaties were replaced, and Indian lands were left vulnerable to a
dramatically increasing population of settlers from outside.

In 1905, the U.S. Senate declassified the 18 treaties negotiated in 1850-52.

For additional and related details on these matters, see this federal case:
Karuk Tribe v.
Ammon, 209 F.3d. 1366 (Fed.Cir. 2000).  
These contents are for general education
and are not to be construed as legal advice.
Honoring Treaties