The only huge legal loophole is “Family Reunification,” which allows an unlimited annual quota for family members of legal immigrants already in the USA.
Also - maybe - ending “Anchor Babies,” which may require an explicit Supreme Court decision, or a Constitutional Amendment.
Trying to close those issues legislatively will be almost impossible because of a Senate filibuster, or, because of a presidential veto, if a Democrat is in the White House.
Almost everything else - universal E-Verify, mass deportation of DACA kids, refugee quotas, work visa quotas - every one of those can be implemented or changed by Executive Order, because there are already laws that clearly apply to them.
Trump has the Executive authority to start deporting DACA kids any day he wants to - the "D" in DACA stands for "Deferred Prosecution."
Unfortunately, Trump has made it quite clear that he is only going to deport criminal DACAs.
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“Anchor Babies” are imaginary.
The 14th amendment specifically demands that parents be here legally (under the authority) before children born here are elligible for citizenship.
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