In the case of Woodby v. Immigration and Naturalization Service, 1966, the U.S Supreme Court ruled that in deportation proceedings, the government must provide "clear, unequivocal and convincing" evidence to justify an individual's expulsion from the country. The court held that this standard was higher than a mere preponderance of evidence but less stringent than beyond reasonable doubt required in criminal cases. This decision arose when Mr. Woodby challenged his deportation order on grounds that he had not been proven deportable by clear and convincing evidence as per due process requirements under Fifth Amendment rights. The ruling significantly impacted immigration law by establishing a high burden of proof for the government in deportation proceedings.

In the dissenting opinion for Woodby v. Immigration and Naturalization Service, Justice Harlan disagreed with the majority's decision to apply a "clear, unequivocal, and convincing" standard of proof in deportation proceedings. He argued that this higher burden of proof was not required by either the Constitution or federal immigration law. Instead, he believed that Congress intended for a lower "preponderance of evidence" standard to be used in such cases. This would mean that an individual could be deported if it is more likely than not they violated immigration laws - rather than requiring almost absolute certainty as under the stricter standard adopted by the majority. Justice Harlan also expressed concern about how this heightened requirement might hinder effective enforcement of immigration policy.