In the case of Lem Moon Sing v. United States in 1894, the U.S Supreme Court upheld a decision that denied re-entry to a Chinese merchant who had previously lived and worked in San Francisco but returned to China for a visit. The court ruled that Congress has plenary power over immigration policy and can make laws which are retroactive, affecting individuals who have left the country with an intention to return. This ruling was based on an interpretation of the Geary Act (1892), which extended previous restrictions on Chinese immigration by requiring all Chinese residents in America to carry certificates of residence or face deportation. Although Lem Moon Sing argued he was exempt from these requirements because he held a certificate allowing him reentry under earlier legislation, his appeal was rejected as it conflicted with later regulations imposed by Congress.

In the dissenting opinion for Lem Moon Sing v. United States, Justice Brewer argued that the majority's decision was a misinterpretation of both the Geary Act and constitutional law. He contended that Congress did not intend to exclude Chinese residents who had left before the act was passed and returned after its enactment, as this would be an ex post facto law - something prohibited by the Constitution. Furthermore, he asserted that even if Congress intended such exclusion, it would still be unconstitutional because it deprives individuals of their liberty without due process of law. Therefore, in his view, Lem Moon Sing should have been allowed re-entry into America based on his prior residence status alone.