In Blackmar v. Guerre, the U.S. Supreme Court ruled in 1951 that federal employees must comply with state laws regarding professional qualifications unless those laws interfere with the performance of their federal duties. The case involved a Veterans' Administration attorney who was practicing law in Louisiana without being admitted to its bar association or meeting other state requirements for lawyers. He argued that his position as a federal employee exempted him from these requirements, but both lower courts and ultimately the Supreme Court disagreed. The court held that while Congress could grant such an exemption if it chose to do so, it had not done so in this instance and therefore he was required to meet all applicable state regulations.

In the dissenting opinion for Blackmar v. Guerre, Justice Frankfurter argued that the majority's decision was a departure from established principles of administrative law and statutory interpretation. He contended that the Veterans' Administration (VA) had been given broad authority by Congress to administer veterans' benefits programs, including determining eligibility criteria. The VA's interpretation of its own regulations should therefore be given deference unless it is clearly wrong or unreasonable, which he did not believe was the case here. Furthermore, he disagreed with the majority's view that Mr. Guerre could not waive his right to receive full compensation under federal law because this would undermine congressional intent to provide maximum benefits for veterans; instead, he believed such waivers were permissible as long as they were made knowingly and voluntarily.