The problem for the Trump administration is that there were the legal equivalents of undocumented immigrants living in the United States at the time of the writing and ratification of the 14th Amendment: those Black Americans, free and freed, who had been illegally imported into the United States after 1808, when the law banning American participation in the trans-Atlantic slave trade took effect. As Gabriel J. Chin and Paul Finkelman observed in a 2021 article for The UC Davis Law Review, both federal and state governments used the tools of modern day immigration enforcement — interdictions, deportations and restrictions on internal migration — in an attempt to deal with the problem. Congress could have excluded these unauthorized residents and their children from the 14th Amendment. They did not.
More striking is the fact that the Republican Party that spearheaded the 14th Amendment contained a sizable number of former Know-Nothings — members, that is, of the nativist American Party that opposed Catholic and Chinese immigration to the United States. It is difficult to believe that the authors of the 14th Amendment were unaware of these attitudes or blind to the possibility that they would grant citizenship to the children of the targets of nativist hate.
In fact, when asked if the clause would “have the effect of naturalizing the children of Chinese and Gypsies born in this country,” Senator Lyman Trumbull, who helped draft the language of birthright citizenship in the Civil Rights Act of 1866 — which the 14th Amendment was written to secure and affirm — replied, “Undoubtedly.” Senator John Conness of California said outright that he was “ready to accept the provision proposed in this constitutional amendment, that the children born here of Mongolian parents shall be declared by the Constitution of the United States to be entitled to civil rights and to equal protection before the law with others.”
The other path the administration could take, if it hasn’t already, is to say that undocumented immigrants constitute an invasion by “enemies within and during a hostile occupation of part of our territory,” as per the court’s language in Wong Kim Ark. But this, too, is a novel understanding belied by the historical record. The word “invasion” appears, among other places, in Article I, Sections 8, and Article IV, Section 4, as part of the militia clause and the guarantee clause.
In using this term, the framers and ratifiers of the Constitution were almost certainly leaning on the definition offered by Samuel Johnson, the English writer and lexicographer, who defined an “invasion” as a “hostile entrance upon the rights or possessions of another” or a “hostile encroachment.” It strains credulity to describe illegal border crossings — by overwhelmingly peaceful migrants — as anything hostile or aggressive. Even the conservative Texas Public Policy Foundation, in a 2022 report on the meaning of “invasion” in the Constitution, concluded that “the unlawful entry of people into the United States cannot be construed as an invasion. Nor, for the same reason, can the prospect of further illegal entry in the imminent future be so construed.”