Article I, Section 8, Clause 18:
[The Congress shall have Power . . . ] To make all Laws which shall be necessary and proper for carrying into Execution the foregoing Powers, and all other Powers vested by this Constitution in the Government of the United States, or in any Department or Officer thereof.
Long-standing Supreme Court precedent recognizes Congress as having plenary power over immigration, giving it almost complete authority to decide whether foreign nationals (aliens, under governing statutes and case law) may enter or remain in the United States.1 But while Congress’s power over immigration is well established, defining its constitutional underpinnings is more difficult. The Constitution does not mention immigration, but parts of the Constitution address related subjects. The Supreme Court has sometimes relied upon Congress’s powers over naturalization (the term and conditions in which an alien becomes a U.S. citizen),2 foreign commerce,3 and, to a lesser extent, upon the Executive Branch’s implied Article II foreign affairs power,4 as sources of federal immigration power.5 While these powers continue to be cited as supporting the immigration power, since the late nineteenth century, the Supreme Court has described the power as flowing from the Constitution’s establishment of a federal government.6 The United States government possesses all the powers incident to a sovereign, including unqualified authority over the Nation’s borders and the ability to determine whether foreign nationals may come within its territory.7 The Supreme Court has generally assigned the constitutional power to regulate immigration to Congress, with executive authority mainly derived from congressional delegations of authority.8
In exercising its power over immigration, Congress can make laws concerning aliens that would be unconstitutional if applied to citizens.9 The Supreme Court has interpreted that power to apply with most force to the admission and exclusion of nonresident aliens abroad seeking to enter the United States.10 The Court has further upheld laws excluding aliens from entry on the basis of ethnicity,11 gender and legitimacy,12 and political belief.13 It has also upheld an Executive Branch exclusion policy, premised on a broad statutory delegation of authority, that some evidence suggested was motivated by religious animus.14 But the immigration power has proven less than absolute when directed at aliens already physically present within the United States.15 Even so, the Supreme Court’s jurisprudence reflects that Congress retains broad power to regulate immigration and that the Court will accord substantial deference to the government’s immigration policies, particularly those that implicate matters of national security.
