In the case of United States v. Kokinda et al., 1989, the U.S Supreme Court ruled on whether a regulation prohibiting solicitation on postal premises violated the First Amendment rights to free speech. The defendants were members of a political advocacy group who had set up a table outside a post office in order to solicit contributions and distribute literature. They were convicted for violating federal regulations that prohibited such activities without permission from postal authorities. In their defense, they argued that these regulations infringed upon their constitutional right to freedom of speech. The Supreme Court upheld their convictions by ruling that although public forums generally have broad protections under the First Amendment, not all property owned or controlled by government is considered as such; some are classified as nonpublic forums where restrictions can be imposed if reasonable and viewpoint neutral. The court found this particular post office sidewalk was not typically used for general public discourse but specifically intended for customers' use in transacting postal business only - thus classifying it as nonpublic forum where solicitation could reasonably be restricted due to its disruptive effect on business operations.

In the dissenting opinion for United States v. Kokinda, Justice Brennan argued that the majority had incorrectly applied public forum doctrine and mischaracterized the nature of postal sidewalks. He asserted that these sidewalks should be considered traditional public forums because they are indistinguishable from municipal sidewalks, which have long been held as such. Therefore, restrictions on speech in this context should be subject to strict scrutiny rather than a less rigorous standard of review. Brennan also disagreed with the majority's view that solicitation is inherently disruptive to post office business; he believed there was insufficient evidence to support this claim and suggested it was merely speculative. Furthermore, he criticized the majority for failing to consider whether less restrictive alternatives could adequately serve governmental interests while preserving First Amendment rights.