Supreme Court Blocks 'Trump Too Small' Trademark Attempt

A California man seeking to lock up the rights to a Donald Trump dig just took a legal L in the highest court in the land ... but he can still sell his shirts with the suggestive phrase.

The Supreme Court just unanimously rejected Steve Elster's bid to trademark the phrase "Trump Too Small" ... which he's been using on t-shirts going for $25 a pop.

Elster, a lawyer in California, tried to trademark the phrase but was rejected by the U.S. Patent and Trademark Office ... and then he claimed his First Amendment rights had been violated, appealing the case all the way to SCOTUS ... which ultimately heard the case.

On Thursday, the ruling came down from the Justices ... with Clarence Thomas saying Elster did NOT have his First Amendment rights violated because of a documented history of trademarks being rejected when they include names of living persons without consent.

The phrase derives from Trump's beef with Marco Rubio during the 2016 presidential campaign ... when Trump labeled Rubio "little Marco" and Rubio responded by saying, "Have you seen his hands? And you know what they say about men with small hands."

Trump punched back in a 2016 debate, telling viewers ... "Look at those hands. Are they small hands? And he referred to my hands -- if they're small, something else must be small. I guarantee you there's no problem. I guarantee you."