An Uber official who asked not to be named confirmed that the real target of the suit is Chicago.

“We believe the lawsuit should bring clarity to fees around the state, including Chicago,” that source said. “Our belief is that the Illinois Constitution forbids any municipality in Illinois from imposing (such a tax). A positive ruling in this case would likely impact Chicago.”

The Skokie tax, adopted in May, charges a flat fee of 35 cents for each individual trip and 15 cents for each shared ride that begins or ends in Skokie. Lightfoot’s plan would convert the city’s across-the-board levy of 72 cents a ride into one that varies by location, with trips to the central area charged the most.

The core of Uber’s argument, filed by attorneys from Jenner & Block and Massey & Gail, is that taxes generally ought to be uniform statewide lest they “create serious problems,” the latter phrase appearing in a 1982 Illinois Supreme Court decision. “Taxes in other states are uniform and Uber has never contested the legal validity of such a tax,” Uber's court filing says.

Beyond that, it argues, the Skokie tax specifically violates provisions of the Illinois Constitution by illegally taxing an occupation (operating a ride-hailing company), extending to trips that may be partially outside of the village and imposing the fee without justification.

On the latter point, the suit points out that Skokie officials asserted in passing the tax that it would compensate the village for increased use of its roads. That bears a rough similarity to Lightfoot’s argument that much of a reported increase in downtown congestion is due to ride-hailing vehicles. Uber has challenged Lightfoot’s numbers, saying they are inflated.

Uber has not previously sued over taxes in Illinois, but it is challenging a New York law that caps the number of ride-hailing cars that can operate, especially in certain crowded Manhattan neighborhoods. The company has been sued here in Illinois by the agency that operates McCormick Place over taxes on trips from Chicago airports.

Uber is not saying why it sued Skokie rather than Chicago, which has had a ride-hailing tax for some years. But the city certainly is in a better position financially than the village to hire expensive legal talent in a case that could end up going all the way to the Illinois Supreme Court.

Potential legal problems with Lightfoot's Uber tax is only the latest budgetary woe the mayor faces. Aldermen have raised questions about a $200 million refinancing plan included in the budget, and her call to raise $50 million next year by increasing the city’s real estate transfer tax faces major opposition in Springfield.