In the Piemonte v. United States case of 1960, the Supreme Court ruled that a defendant's right to counsel was not violated when he voluntarily waived his right and pleaded guilty without legal representation. The petitioner, Joseph Piemonte, had been indicted on charges related to narcotics violations. He appeared in court without an attorney and entered a plea of guilty after being informed by the judge about his rights including having an attorney appointed for him if he couldn't afford one. Later on, Piemonte appealed claiming that his constitutional rights were violated because he didn’t have legal representation during this process. The Supreme Court disagreed with Piemonte’s argument stating that there is no absolute requirement for counsel when a competent defendant willingly foregoes their right to it under proper judicial supervision. The court held that since Piemonte was fully aware of his situation and consequences thereof but still chose to proceed without an attorney; hence there wasn't any violation of Sixth Amendment Rights which guarantees every criminal defendant assistance from counsel in defending themselves.

In the dissenting opinion for Piemonte v. United States, Justice Brennan argued that the majority's decision to uphold Piemonte's conviction was a departure from established precedent regarding entrapment. He contended that there was sufficient evidence to suggest that government agents may have induced Piemonte into committing the crime, and therefore, it should be up to a jury - not judges - to decide whether or not this constituted entrapment. Furthermore, he criticized the majority for failing to adequately consider how their ruling might encourage law enforcement agencies to engage in questionable tactics in order to secure convictions. In his view, such practices could potentially undermine public trust in law enforcement and erode civil liberties.