The Supreme Court case of UNITED STATES ex rel. BILOKUMSKY v. TOD, Commissioner of Immigration at the Port of New York, et al. established the legal principle that in deportation proceedings, the burden of proving alienage rests on the government. The Court held that although alienage is a jurisdictional fact that must be established for a valid deportation order, the government bears the burden of proving the alien status of the individual facing deportation. This ruling was significant as it protected the due process rights of individuals by requiring the immigration authorities to demonstrate the factual basis for their deportation orders, rather than placing that burden on the individual. The Court's decision in this case reaffirmed the importance of safeguarding the fundamental rights of those facing potential removal from the United States, even when they are not U.S. citizens.