It already is a criminal act

>My son heard on the radio that in the United States they want to declare it a criminal act, for an alien to be in the United States without documentation, or something of the sort. He asked: "Wasn't it a criminal act, already?" To the best of my knowledge, I answered that I assume that aliens can be thrown out of the country for being there without a permit, but that they can't be otherwise prosecuted and thrown into prison. Is the news he heard correct? Is this my understanding of the situation correct?
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>My son heard this news in Spanish; would the word "felony" be used in English?
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>TIA,
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>Hilmar.