Updated: Sep 20, 2020
The Bill of Rights applies to every non-citizen in American territory. This is because nowhere in the Bill of Rights does it say "citizen", it only says "people" and "person". Therefore, the Bill of Rights applies to any "person" on American soil, even illegal immigrants, as they are "people".
In the justice system, illegal immigrants have the same due process as any other citizen who has committed a crime. They both have rights such as the right to a trial by jury and an attorney. Whether you are an American citizen or an illegal immigrant being prosecuted for say, selling 15 kilograms of methamphetamine, the trial procedure is the same. This ensures equality under the law -- a positive.
However, what about the right to family integrity (not separating a family) or the right to education? Do non-citizens attain these rights when in America?
Yes, they do. Although some rights such as the right to family integrity and education are not expressed in the Constitution, they have been established though court rulings.
For example, in the 1982 U.S Supreme Court case Plyer v. Doe, the court revised the law that prohibited children of undocumented immigrants from attending school. They ruled that "one's immigration status is not a sufficient rational basis for denying benefits afforded to other residents." Thus, due to this Supreme Court ruling, children of undocumented immigrants now have the right to a K-12 education in America.
On the other hand, there are limitations. Illegal immigrants don't get everything from America. They can't vote, run for office, and when it comes to due processes, deportation, and the right to unreasonable searches, it gets muddy.
For instance, the Fourth Amendment in the Bill of Rights states that any person on U.S territory has the right to be free from unreasonable searches. However, if you are at an airport or at a border, America's constitutional rights do not apply to you because you are technically not on U.S territory.
Additionally, as expressed in the Illegal Immigration Reform and Responsibility Act of 1996, illegal immigrants in the country for less than two years and apprehended within 100 miles from the border can be deported immediately with out a proper hearing. While that almost crosses the line of constitutional jurisdiction, it is a legal statute.
The aforementioned process of deportation is called expedited removal which is a favorite processes of Donald Trump because, according to him, "when somebody comes in, we must immediately, with no judges or court cases, bring them back from [to] where they came." Here, Trump is most likely hinting at the statute of expedited removal as evident in the phrase "no Judges or Court Cases," but we will never know as this tweet is yet another one of Trump's infamous, misleading statements.
In summary, if you are in America illegally, there are lots of constitutional laws that protect you. However, there are also many more ways the government can legally deport you and target you, as Trump does.