MoonBatman

Where in the US constitution does it guarantee protections to those who are not citizens?
I’m happy you asked, you’re going to get a real answer because of that.
The Constitution specifically and explicitly guarantees due process and the equal protection of the law to non-citizens in the Fourteenth Amendment:
All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the state wherein they reside. No state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any state deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.
A big piece of this worried that states might try to go back to some form of slavery, or at the very least end up doing a lot of discriminating, by essentially stripping people of their state citizenship, which was precisely what was happening in 1868.
First, it’s important to note that the infamous Supreme Court decision in Dred Scott v. Sanford had not yet been overruled - there were black people in the United States that were not considered citizens. There was also the matter of the decision in Barron v. Baltimore that stated that the Federal Constitution did not apply to the individual States except where expressly stated. Because of these two decisions, States could abridge free speech, free press, perform searches on black homes without legal recourse, lynch blacks that stepped out of line, and more.
That’s why after the Civil War and the passage of the 13th Amendment, Southern states immediately moved to adopt “black codes” that severely restricted the rights of the newly freed blacks so as to essentially place them back in at least the social standing of slavery. White Southerners passed laws restricting the rights of blacks to own real or personal property, to form contracts (meaning whites couldn’t be bound to contracts entered into with blacks,) and instituting severely harsher criminal penalties - essentially jaywalking could get you a death sentence. This was justified because blacks were not citizens either of the individual States nor of the United States and therefore entitled to no rights under either the federal or various state constitutions.
In response, Congress passed the Civil Rights Act of 1866, which would have granted full citizenship to all former slaves and essentially to all people currently in the United States. The Southern states fought it bitterly, contesting the constitutional basis of its passage. President Andrew Johnson agreed and vetoed the law.
Enraged by this, Congressional Republicans, who were excluding Southerners from Congress at the time as not having been readmitted to the Union with representation in Congress, drafted the Fourteenth Amendment, and in particular the Equal Protection and Due Process Clauses, both of which are expressly targeted at the individual States themselves. They required ratification of this amendment as part of the Southern re-entry into congressional representation.
Section 1 of the 14th Amendment first guarantees citizenship to “all persons born or naturalized in the United States.” However, the Republican drafters of this language were worried that white Southerners could interpret this to exclude any African-born slaves, or even to black people born after secession, and that’s why the drafters went a step further to make sure that the equal protection clause applied to anyone in the jurisdiction of the United States. That’s why the equal protection clause is explicitly guaranteed to “all persons within its [each State’s] jurisdiction.”
Thanks for pointing out that certain people remained excluded for a good long while after this. Native Americans were not granted citizenship until 1924 under the American Indian Citizenship Act and could be legally excluded barred from voting by states until 1957.
Aha! you might think - these all explicitly apply only to the states! So the federal government, which exclusively oversees immigration and non-citizen residents, would not be bound by such language! Unfortunately for such an interpretation, the Supreme Court has ruled in Bolling v. Sharpe and more recently opined in dicta in Lawrence v. Texas that the Fifth Amendment requires the same equal protection of the laws under the Federal government.
(Note: while the Court has ruled that the Fifth Amendment requires equal protection of the laws of the Federal government, the Federal government exclusively has jurisdiction over dealings with the Native American tribes, and that continues even today to be a poor and discriminatory relationship that does not particularly reflect either due process or equal protection. But I digress.)
Now, resident aliens and undocumented immigrants are not granted the entire range of rights granted to full citizens and the court has been somewhat inconsistent on the subject. The Supreme Court has allowed restrictions on voting in federal elections and state laws requiring public school teachers to be citizens and from being public notaries. The Court has struck down laws banning resident aliens and undocumented immigrants from attending public schools and laws requiring citizenship for bar applications to become a lawyer. It is unclear as to what level of scrutiny is applied to review of these laws; in some cases, the Court has applied strict scrutiny, in others, it has applied something like a heightened intermediate scrutiny.
Lastly, there is a very good reason to grant non-resident aliens due process and equal protection: the civil rights of actual citizens. If due process and equal protection are suspended whenever a person is suspected of being an undocumented immigrant, it is only a matter of time before actual U.S. citizens, naturalized or natural-born, are going to be caught up in the process and have their civil rights abridged while they are forced to prove their citizenship. This has already happened, even and especially recently.[1][2]
Some people might argue, “Oh, that’s fine. I’ll just pull out my driver’s license.” Would that be good enough to satisfy a Border Patrol or ICE agent that knows such things can be obtained fraudulently? Perhaps a birth certificate? Passport? This is the problem that voter ID laws face that require some sort of “proof of citizenship”: they disproportionately affect certain groups of actual citizens who cannot afford to get the appropriate papers. Any policy of “papers please or have due process and equal protection suspended” will, as sure as I stand here, lead to an innocent full citizen having their rights trampled by the government.
As soon as the law doesn’t protect everyone, abusive governments will start to put people into unprotected categories, every single time, as many times as you care to run the experiment. Even with the explicit guarantee of equal protection in the United States, civil rights have been abridged for various racial minorities on many different occasions.
The minute we start to categorize people into “illegals” and start to associate “illegals” with “brown-skinned folks who speak something other than English,” and those people don’t get equal protection and due process, we are all damaged by it. And it becomes just a matter of time before an innocent person suffers because of it.
For these myriad reasons, the Supreme Court has been clear in the application of the law to non-citizens in the United States: the Fourteenth Amendment guarantees equal protection of the law to them............[1] https://taskandpurpose-com.cdn.ampproject.org/…/im-us…/amp/…
[2] http://www.krtv.com/…/us-citizen-questioned-by-border-patro…