The U.S. Supreme Court recently seemed to struggle with rules for trademarking generic names that are combined with the .com phrase.

According to the National Law Journal, many justices seemed to agree with an attorney for that a 132-year-old Supreme Court precedent probably doesn’t control the case. But they also sounded wary of granting an online monopoly over entire categories of goods and services, and that it could lead to a flood of litigation over similar sounding names.

Without federal registration, a valid trademark can still be enforced against would-be infringers. But federal registration confers additional legal rights and benefits. It provides constructive notice of the mark, it can become incontestable once registered for five years, and the trademark holder can stop the importation of counterfeits.

A longstanding rule of trademarks is that generic names cannot be registered. The PTO argues that adding .com isn’t enough to make a generic mark descriptive and potentially eligible for registration. The agency is invoking an 1888 Supreme Court ruling, Goodyear’s India Rubber Glove Mfg. v. Goodyear Rubber, that adopted a similar rule for the addition of “Company” or “Inc.” to a name. More recently, the U.S. Court of Appeals for the Federal Circuit has upheld the PTO’s refusal to register and, and the U.S. Court of Appeals for the Ninth Circuit has found AOL’s generic.

Pillsbury Intellectual Property partner William Atkins, who like many listened the arguments live on C-SPAN, said it was a pleasant surprise to hear Justice Thomas ask not one, but numerous questions.

“It was great to hear Justice Breyer follow up Justice Thomas’ question about why one can register a 1-800 number as a trademark and yet not a dot-com,” Atkins said. The government’s response was “not as compelling,” he said.