Complete, absolute, and unqualified power over a particular subject matter, typically referring to Congress's broad constitutional authority in areas like immigration, naturalization, and foreign affairs. When Congress has plenary power, judicial review is extremely limited.
From Latin 'plenus' meaning 'full' or 'complete.' The concept evolved from English parliamentary sovereignty into American constitutional law, particularly in areas where the Constitution grants Congress broad, undefined authority that courts have interpreted as nearly absolute.
Plenary power is Congress's constitutional superpower—in areas like immigration, the Supreme Court has said Congress can do almost anything, even if it seems unfair or discriminatory. This doctrine emerged from 19th-century cases involving Chinese exclusion and has been controversial because it allows immigration laws that would be unconstitutional if applied to citizens. The tension between plenary power and individual rights continues to shape debates over immigration policy and national security.
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