Imagine Obama issues an executive decree, or Congress passes a law, that says nobody can worship on Sundays without a permit. Without "documentation." Without papers.
I would never call anyone who violated this law and worshipped on Sunday an "illegal worshipper," or an "undocumented worshipper." This is because there is no Constitutional authority for such a law. Such a law is unconstitutional.
There is nothing in the Constitution which empowers the federal government to require papers or a federal stamp of approval before a Mexican can enter the U.S. It's not in the Constitution. Nowhere.
Just as America's Founding Fathers ignored the British "Stamp Act," so "illegal" aliens more embody "the Spirit of '76" than those who apply for the government stamp of approval before entering the U.S.
Tragically, some "illegal aliens" have as little respect for private property and the rule of law as many natural-born American citizens, and especially those who work in Washington, D.C.