In the case of Flower v. United States (1971), the U.S. Supreme Court overturned a conviction for trespassing on a military base in Texas. The defendant, John Francis Flower, had been distributing anti-war literature on a public road within Fort Sam Houston without causing any disruption or breach of peace. He was charged with violating an order from the commanding officer prohibiting such activities and convicted by lower courts. The Supreme Court ruled that since the road where Flower distributed his materials was open to unrestricted civilian traffic and indistinguishable from city streets, it constituted a public forum despite being located within military property boundaries. Therefore, as per First Amendment rights guaranteeing freedom of speech and expression, Mr.Flower's actions were protected unless they posed some substantial risk to operational effectiveness which wasn't proven in this case. This decision underscored that even though military bases have special considerations regarding security and discipline; constitutional protections still apply when areas are made accessible to general public use.

In the dissenting opinion for Flower v. United States, Justice Hugo Black argued that the majority's decision was a misinterpretation of public property rights and First Amendment freedoms. He contended that Fort Sam Houston, despite being a military base, was still subject to constitutional protections because it functioned as an open public space where civilians could freely enter and leave. Therefore, he believed Mr. Flower had every right to distribute anti-war literature there without facing criminal charges. Furthermore, Justice Black criticized the majority for failing to distinguish between peaceful protest activities and actions that genuinely threaten national security or disrupt military operations - a distinction he considered crucial in maintaining both civil liberties and defense interests in such contexts.