Eric Goode, 59, is a New York entrepreneur who is an owner of downtown establishments like the Bowery Hotel and the Waverly Inn. He was a creator of Area, the art-gallery-nightclub from the 1980s. He is also a conservationist with something of an obsession for turtles.

And now he is the plaintiff in a federal lawsuit that accuses President Trump of violating the Emoluments Clause of the Constitution, a once-obscure provision intended to prevent federal officials, including the president, from falling under the influence of foreign powers.

Mr. Goode is an unlikely, reluctant and unusually prominent plaintiff in the high-stakes constitutional lawsuit. “I do question the wisdom of it,” he said over a cappuccino in the lobby of the Bowery Hotel, which looks like a British manor’s library with a rain forest growing in it. “Hopefully I am not going to get audited and harassed for the next three years, but it seemed like the right thing to do. I’m worried about veiled forms of retribution.”

He was just back from a Rainforest Trust board meeting in Virginia and was headed to the West Coast outpost of his Turtle Conservancy in Ojai, Calif., where Galápagos tortoises and other creatures, some of which he has helped rescue from the black market, roam safely. His celebrity friends come there to roam, too. Their specific breeds, he doesn’t want to mention.