In the case of Gary E. Peel v. Attorney Registration and Disciplinary Commission of Illinois, 1989, attorney Gary E. Peel was disciplined by the commission for professional misconduct related to his divorce proceedings with his ex-wife. The disciplinary action stemmed from a letter that Mr. Peel sent to his ex-wife's husband in which he threatened to publicize explicit photographs taken during their marriage unless she agreed to modify their property settlement agreement in his favor. The Supreme Court ruled against Mr. Peel on First Amendment grounds, stating that while attorneys have free speech rights like any other citizen, they also have ethical obligations as officers of the court not to engage in conduct involving dishonesty or misrepresentation or behavior prejudicially affecting the administration of justice. Therefore, it held that an attorney can be disciplined for threatening litigation solely for obtaining an advantage unrelated to legal process and using means having no substantial purpose other than embarrassing or harming another person.

In the dissenting opinion for Gary E. Peel v. Attorney Registration and Disciplinary Commission of Illinois, Justice Brennan argued that the majority's decision was a violation of Peel's First Amendment rights to free speech. He contended that there is no compelling state interest in preventing an attorney from advertising truthful information about his or her professional credentials, such as being certified as a specialist by a nationally recognized organization. The justice further stated that the court’s ruling could lead to arbitrary enforcement and potential abuse since it allows disciplinary action against attorneys who advertise legitimate certifications while permitting those with less meaningful qualifications to do so without repercussions. In essence, he believed this case represented an unwarranted restriction on commercial speech which should be protected under the First Amendment.