To get a drivers license you have to declare that you are "a citizen of the united states" and a "citizen of the state of X".
We, as people, choose our society. (look up the definition of person, people, and society in bouvier's law dictionary)
This means that, by choice, the "illegal immigrants" are declaring themselves to be US Persons. By doing so they become such... even though a person is not a people.
Once done, you are no longer an undocumented alien... but as a matter of law a document US Person.
Your declaration (decision) determines what you are.
What if all of the people of the several states of the united States decided that they were, in fact, NOT US Persons?
Are you a corporation? Do you belong to the US corporation?
Is it required to declare loyal to America? If so, the status of illegal immigrants is no longer valid. Once there is a document they are American citizens.