In the 1957 case Nowak v. United States, the Supreme Court ruled on a matter involving citizenship and naturalization laws. The petitioner, Walter Nowak, was born in Germany to Polish parents who later became naturalized U.S citizens while he was still a minor. As an adult, Nowak renounced his U.S citizenship at a consulate in Mexico before returning to live in America for several years under an assumed name. He then applied for admission as an alien immigrant but was denied due to his previous criminal record and deportation proceedings were initiated against him. Nowak argued that he had never legally been a citizen of the United States because his parents' naturalization occurred after he turned eighteen - thus making it impossible for him to lose what he claimed not having possessed initially. However, the court found that since both of his parents were indeed American citizens when they arrived back from Poland (while Walter was still underage), their son automatically gained US nationality according to existing immigration law at that time. The Supreme Court upheld this decision stating that once acquired; American citizenship could only be relinquished voluntarily and with intent – neither of which applied here given Mr.Nowak's age during parental naturalization.

In the dissenting opinion for Nowak v. United States, Justice Brennan disagreed with the majority's decision to deny citizenship to a Polish immigrant who had been convicted of two crimes involving moral turpitude. He argued that the court was misinterpreting and overstepping its bounds in applying immigration law, specifically regarding what constitutes "good moral character." According to Brennan, Congress intended for this term to be applied flexibly on a case-by-case basis rather than as an absolute standard. Furthermore, he contended that it was not within the Court’s purview to decide whether or not someone is morally fit for citizenship based on past criminal behavior alone; instead, such decisions should take into account other factors like rehabilitation and current conduct. In essence, Justice Brennan believed that denying Nowak his citizenship due solely to his prior convictions violated both legislative intent and principles of fairness.