In the case of In re Griffiths (1972), the U.S. Supreme Court ruled that a state cannot deny an individual the right to practice law based on their citizenship status. The plaintiff, Gwendolyn E. Griffiths, was a resident alien who had passed her bar examination in Connecticut but was denied admission to practice because she wasn't a U.S citizen as required by state law. She challenged this requirement as unconstitutional under the Equal Protection Clause of Fourteenth Amendment which prohibits states from denying any person within its jurisdiction equal protection under its laws. The court held that barring non-citizens from practicing law is not related to an applicant's fitness or competence and thus violates their rights for equal protection under laws guaranteed by 14th amendment.

In the dissenting opinion for In re Griffiths, Justice Rehnquist disagreed with the majority's view that a state cannot exclude non-citizens from practicing law. He argued that states have historically had broad discretion to determine qualifications for those wishing to practice law within their jurisdictions and this should include citizenship requirements. He contended that such requirements are not inherently discriminatory but rather serve legitimate state interests in ensuring loyalty and commitment to the U.S Constitution among its legal practitioners. Furthermore, he suggested that if any changes were needed regarding these rules, they should come through legislative action rather than judicial intervention. Thus, he believed it was inappropriate for courts to interfere with states' rights in regulating professions like law.