Yet, this authority to regulate commerce with the tribes has been transformed into a plenary power over Indian affairs, almost without limits. Obviously, the federal government must operate within the boundaries of the United States Constitution in its dealings with tribal nations. However, while the federal government uses its plenary power and trust responsibility as a shield for tribes and their sovereignty, through its duty and power it also wields a mighty sword. The federal government has a trust responsibility to protect tribes, yet Congress' power has been interpreted to be great enough to unilaterally abolish treaties or certain treaty rights, and to end the government-to-government relationship with any particular tribe. At its most extreme limits, Congress can legislate who is and is not an Indian tribe. Congress also has the power to increase, decrease, or remove entirely from tribal governments their criminal and civil jurisdiction. Congress also has the power to export into Indian Country federal criminal laws due to its plenary power. The relationship between Congress and Indian tribes is complex. Often the duties and powers of Congress, in relation to the tribes, conflict with each other. When such conflicts arise regarding the