Spiro is representing New York developer Property Markets Group in its lawsuit against the city over the Pilsen downzoning. In 2016, Ald. Solis killed a plan by the developer for a 465-unit apartment project in the South Side neighborhood by pushing a proposal through City Council to switch the zoning on the development site from residential to industrial. Though Property Markets Group was legally entitled to build the project under the prior zoning, it refused to acquiesce to demands by Solis to add extra affordable housing beyond what the city ordinance required.

Solis, who is not a defendant in the suit, said last February that his push for additional affordable housing was "something that I want to do for my community of Pilsen." Last month, he resigned as chairman of the City Council's powerful zoning committee after the Chicago Sun-Times reported that Solis had pressured a developer who wanted to build a hotel in his ward to hire Illinois House Speaker Michael Madigan's law firm for property tax appeals work. Solis has not been charged any wrongdoing.

A spokesman for the city's Department of Law declined to comment on any downzoning litigation, saying the department has a policy of not discussing pending lawsuits.

Downzoning can be a force for good. When developers were stamping out dozens of tall high-rises in lakefront neighborhoods on the North Side in the 1960s and 1970s, the city, aiming to preserve the older, low-rise housing stock in the area, reined in development by reducing the zoning in large sections of the neighborhoods. City officials took similar actions to curb construction of controversial four-plus-one apartment buildings in the early 1970s.

"I think it was good public policy," says DePaul University professor Joseph Schwieterman, director of the school's Chaddick Institute for Metropolitan Development and author of the 2006 book "The Politics of Place: A History of Zoning in Chicago."

But those changes covered multiple city blocks and resulted from an extended debate among city officials, neighborhood groups and other stakeholders. What happens today is too often arbitrary: A single alderman will decide the fate of a property, with motives that aren't always clear, Schwieterman says. And by drastically reducing what can be built on a property, an alderman can slash its value with the stroke of a pen.

Under aldermanic privilege, none of the alderman's 49 colleagues in City Council will vote against a downzoning proposal. Why? They don't want any alderman to oppose a similar proposal of theirs.

"It creates real uncertainty for real estate developers when downzoning becomes ad hoc or driven by the desire of an alderman to settle scores," Schwieterman says.

Property owners contend it also violates their constitutionally protected property rights, an argument they make in their lawsuits against the city.

But that doesn't deter aldermen in places like Humboldt Park or Logan Square, where many constituents are demanding they take steps to curb rampant development. In 2017, Ald. Carlos Ramirez-Rosa, 35th, proposed downzoning two stretches of Milwaukee Avenue, in Logan Square and in Avondale. The measures are still pending.

In Humboldt Park, Maldonado filed proposals for 22 properties, in most cases reducing the size of the homes that a developer could build on them. Some of the properties are empty lots, logical development candidates. A staffer for Maldonado did not return calls, but the alderman said in a brief December interview that he wants to downzone the properties to ease gentrification.

With an election coming up, that's a move that could pay off at the polls.