The reason not all undocumented immigrants have been deported is partly because U.S. enforcement resources are insufficient to keep up with the numbers. Detaining and deporting even one person costs many thousands of dollars.
It’s also important to understand that there are gray areas, where someone who might be viewed by some as undocumented has what almost amounts to a right to remain in the United States. For example, asylum seekers being sought for persecution by their own government, who are unable to make direct contact with a refugee agency in their own country, might have no choice for U.S. entry but to come illegally. If stopped at the border, they should be allowed to state their claim and, if their fear is found credible, to see an immigration judge.
Or, an asylum seeker who makes it into the United States unseen has one year in which to prepare an application for asylum. Although the person has no actual right to be in the United States during that time, a would-be applicant who is caught and placed into removal proceedings can claim asylum at that point, and might very well be approved for asylum (and one year later, be eligible for a green card).
What’s more, under a policy called “prosecutorial discretion,” various immigrants, such as students and those with close family members in the United States, are supposed to be largely left alone by the immigration authorities, so that the authorities can concentrate on immigrants who are criminals or otherwise a risk to U.S. society. Some of these immigrants may actually be granted a sort of limbo status called “deferred action,” and in some cases a work permit. See, for example, Deferred Action for Childhood Arrivals (DACA).
This policy assumes that the current presidential administration acknowledges the need to prioritize which cases to enforce. However, a Republican administration entering office soon, their apparent goal is to greatly restrict prosecutorial discretion (according to Project 2025).
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