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Plenary Power

The broad authority of Congress over Indian affairs, derived from the Indian Commerce Clause and treaty-making power, subject to trust obligations.

Encyclopedia entry: Plenary Power

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Plenary power refers to complete and exclusive authority over a particular subject matter, constrained only by constitutional limitations. When a governmental body holds plenary power, it may legislate or act within that area without requiring additional authorization. The term frequently describes Congress’s power under the Commerce Clause , Article I, Section 8, Clause 3 of the U.S. Constitution , which grants Congress broad authority to regulate interstate commerce . The Supreme Court has likewise recognized Congress’s plenary power over immigration , including the admission and exclusion of non-citizens, as affirmed in Kleindienst v. Mandel, 408 U.S. 753 (1972) .

[Last reviewed in November of 2025 by the Wex Definitions Team
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Encyclopedia content from Cornell LII Wex (CC-BY-NC-SA 2.5).