In the case of In re Engles, 1892, the petitioner was a German citizen who had been living in America for several years. He sought naturalization but refused to take an oath of allegiance to the United States because he believed it would require him to renounce his loyalty to Germany. The Supreme Court ruled that taking an oath of allegiance did not necessarily mean renouncing one's original nationality and therefore Engles could be naturalized without violating his principles. However, they also noted that if there were ever a conflict between his duties as a U.S. citizen and those owed to Germany, he would be expected to prioritize his obligations towards the United States.

The dissenting opinion in the case of In re Engles, 1892, argued that the petitioner should not be denied his application for naturalization based on his refusal to take an oath to support and defend the Constitution. The dissenting justices believed that this requirement was unconstitutional as it violated freedom of thought and conscience protected by First Amendment rights. They contended that a person's political beliefs or unwillingness to fight did not necessarily mean they would act against U.S. interests if granted citizenship. Furthermore, they pointed out inconsistencies in how this rule was applied; some applicants were allowed citizenship despite their refusal to bear arms due to religious reasons while others like Mr. Engles were denied because of personal convictions against war or violence.