In Silicon Valley, Apple just won big against Samsung in the patent lawsuit of the year, after trading claims and counterclaims of pilfered product ideas. Across the country, in a federal court in Florida, an inventor named Mark Stadnyk is waging a different kind of patent warfare — an ambitious and perhaps quixotic legal foray.

Mr. Stadnyk, who holds a patent on a motorcycle windshield, is suing the United States government, aiming to head off a patent law that he says will favor big companies and hurt lone inventors like himself.

Represented by a prominent Washington lawyer, Mr. Stadnyk filed a suit last month that challenges the constitutionality of legislation that Congress passed last fall, the America Invents Act. Mr. Stadnyk and his lawyer — along with some academics, entrepreneurs and venture capitalists — assert that the legislation is a triumph of corporate lobbying power over the founders’ wishes, and that it threatens America’s stature as the world’s leading innovator.

The present system, one of the nation’s oldest patent principles and called “first to invent,” relies on lab notebooks, e-mails and early prototypes to establish the date of invention. The impending law would overturn that by awarding patents to the inventors who are “first to file” with the United States Patent and Trademark Office.