Last summer, the City of Seattle passed a law that will raise the city’s minimum wage to $15 per hour. But in a bizarre twist, Ronald McDonald and friends are suing the city. On March 10, they’ll be in a federal courtroom, complaining that the new minimum wage violates a constitutional provision that was written to protect newly-freed slaves after the Civil War.

Most people can’t survive on Washington’s current statewide minimum wage of $9.47, let alone the federal minimum wage of $7.25. Even if the sophisticated crew-scheduling software let you work 40 hours a week at $9.47 for every single week of the year, you wouldn’t clear $20,000. In the end, 52 percent of fast food workers end up on public assistance. You’ll find similar stories for other minimum wage workers, such as hotel maids and nursing home assistants.

That’s why the Seattle City Council spent months studying the idea of raising the city’s minimum wage. To be sure, some business leaders made economic arguments against raising the minimum wage. Others agreed with workers that a higher minimum wage would actually benefit business overall, or at least were willing to negotiate. The city council heard the arguments on both sides, evaluated their merits, sweated over the details, and ultimately voted to pass a minimum wage ordinance, which the city’s mayor then signed into law.

That should be the end of the story. But, as too often happens these days, corporate trial lawyers have brought expensive litigation to try to stop the law from going into effect. The International Franchise Association, with assistance from the National Restaurant Association and other industry trade groups, is claiming that the law is not just bad for their bottom line, but actually violates the Fourteenth Amendment to the U.S. Constitution.