WASHINGTON — The Supreme Court heard arguments on Monday in a curious case in which no one dared say the word at the heart of the dispute, which was the brand name of a line of clothing that had been denied federal trademark protection.
Malcolm L. Stewart, a lawyer for the federal government, had come prepared with an elaborate circumlocution, calling the word “the equivalent of the past participle form of the paradigmatic profane word in our culture.”
Erik Brunetti, the owner of the clothing line, has sometimes said that its name, FUCT, stood for “Friends U Can’t Trust.” But the justices seemed persuaded that the term amounted to a vulgarity.
“C’mon,” Justice Samuel A. Alito Jr. told Mr. Brunetti’s lawyer, John R. Sommer. “Be serious. We know what he’s trying to say.”
Justice Alito added that the First Amendment’s ordinary skepticism of laws that make distinctions based on speakers’ viewpoints may not apply to the word.
“Like, 99 percent of the time or 95 percent of the time,” he said, “it’s not used to express what the word literally means. It’s just used to say, ‘I’m mad, I want to get attention.’ It’s like shouting.”
An official at the Patent and Trademark Office denied Mr. Brunetti’s application for federal protection for the term under a 1905 federal law that allows the office to refuse to register trademarks that are “immoral, deceptive or scandalous.”
The justices seemed equally troubled by the law, which several said was both vague and inconsistently applied, and by the consequences of ruling in Mr. Brunetti’s favor, which some said would encourage the use of swear words and the most charged racial epithets.
The case, Iancu v. Brunetti, No. 18-302, was further complicated by a 2017 decision from the court that unanimously struck down a neighboring clause in the same part of the trademark law. That clause denied federal trademark protection to terms that disparage people, living or dead, along with “institutions, beliefs or national symbols.”
In the 2017 case, Matal v. Tam, the court ruled that an Asian-American dance-rock band called the Slants was entitled to federal trademark registration. (The decision also effectively allowed the Washington Redskins football team to register its trademarks.)
The justices seemed to find the provision at issue in Monday’s case more challenging. Mr. Stewart said the government would enforce the challenged provision narrowly in light of the 2017 decision, focusing on terms that are shocking or offensive based on the mode of their expression rather than on the ideas they convey.
Justice Elena Kagan responded that it would be strange for the court to interpret the law’s expansive language — barring “immoral” and “scandalous” terms — based on the government’s promise to enforce it sparingly. “These are very broad words,” she asked skeptically, “but we’re going to pretend that they say something much narrower than they do?”
Justice Stephen G. Breyer said the court should find a way to discourage a small subset of terms that he said have physiological effects on the human body. “It’s stored in a different place in the brain,” he said. “It leads to retention of the word.”
Justice Neil M. Gorsuch seemed sympathetic to that approach, though for a different reason. “There are certain words that are profane and that we, as a matter of civility in our culture, would like to see less of rather than more of,” he said.
Ruth Bader Ginsburg, who is 86, said the young people who bought Mr. Brunetti’s wares may not be offended by the brand name. “A composite of, say, 20-year-olds,” she said, would not find the term particularly shocking.
“Suppose in the niche market that these goods are targeting, the name is mainstream,” she said. “These goods, as I understand it, are meant to attract a particular market, and if we concentrate on that market, from their perception, the word is mainstream.”
Justices Gorsuch and Brett M. Kavanaugh said they were troubled by what Justice Kavanaugh called the “erratic or inconsistent enforcement” of the law, with very similar terms granted protection or not with little seeming rhyme or reason.
Justice Gorsuch said examples cited in Mr. Brunetti’s brief were “remarkably similar,” adding that “I could not myself see a rational line.”
“I don’t want to go through the examples,” he added. “I really don’t want to do that.”