That's not actually a new rule. Apparently dems saw the light about what was going to happen, panicked, and realized they had to do something ... so they followed the law - some of it anyway. I'm constantly amazed by all the clamor to fix immigration policy when nobody was actually enforcing policy to begin with. What does need to be fixed is birthright citizenship - most of the world has already dumped that; if we ended that, it would take a lot of the wind out of illegal migration into the US.
There's a clause in the Constitution that the courts don't get right
"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."
Of course, any person physically in the US is subject to at least criminal "jurisdiction". Otherwise it would be legal for an illegal to murder, rob, or commit any number of offenses; but it's completely stupid to interpret that as anyone here illegally falls under the same Constitutional rights as a citizen. Some of history's dumbest schiff come out of the courts.