From the Document: "Immigration law in the United States has long contained exclusion and removal provisions designed to limit government spending on indigent non-U.S. nationals. (Non-U.S. nationals are referred to as aliens in immigration law.) Under the Immigration and Nationality Act (INA), an alien may be denied admission into the United States or lawful permanent resident (LPR) status if he or she is 'likely at any time to become a public charge' (8 U.S.C. §1182(a)(4)). An admitted alien may also be subject to removal from the United States based on a separate public charge ground of deportability, but this is rarely employed."
CRS In Focus, IF11467
Congressional Research Service: https://crsreports.congress.gov/