Earlier this year, the Trump administration announced that it would expand the list of government benefits it considers when defining a person as a “public charge.” Under the new terms, an immigrant receiving, say, food stamps, emergency cash assistance, or living in public housing may see those benefits count against him when he seeks to upgrade or extend his visa status or apply for citizenship. It was long believed that immigrants to the United States should not impose social burdens and should thus secure local sponsors who could guarantee their expenses until they got settled. The Immigration Act of 1891,...