In 2003, the Illinois legislature passed guidelines saying communities with less than 10% affordable housing needed to provide a plan to address this. Only recently did lawmakers set out consequences for not following this:

A sweeping affordable housing bill, recently passed by Illinois state lawmakers, has strengthened the Affordable Housing Planning and Appeal Act (AHPAA). That law requires cities, with at least 1,000 residents and with less than 10% affordable housing, to submit affordable housing plans to the state. The law also allows for affordable housing developers to appeal the decisions of municipalities who reject their affordable housing proposals. Those appeals are heard by the Illinois Housing Appeals board.

The AHPAA, originally passed in 2003, is intended to encourage affordable housing, but resistance is rampant. As of October 2020, the Illinois Housing Development Authority identified 46 municipalities that met the law’s requirements. At that time, fewer than half had submitted plans or indicated that they intended to do so. Some municipalities cited home rule as the reason why they didn’t comply. The revised law says that doesn’t matter anymore. It gives the Illinois Attorney General enforcement powers, including seeking court relief, if the municipalities continue to flout the law…

Schecter said the next hurdle is getting units built — not just submitting plans. She said deadlines are needed for when municipalities must turn in their plans and by when they must achieve the 10% affordable housing requirement.

I have followed this particular Illinois statute as affordable housing, particularly in wealthier suburban areas, has been a contentious issue for decades. In some places, this has been addressed through court cases; see the example of Mount Laurel in New Jersey. Elsewhere, it is often left to market forces and municipal ordinances, which typically means that few communities explicitly address providing affordable housing (and not just housing for people groups they would like to have in their community) and local leaders and residents push back against living near cheaper housing (see the example of resistance to apartments).

The last paragraph quoted above suggests there is still work to be done. The recent changes suggests there are now consequences if communities do not submit plans. But, I would guess the real goal of the 2003 guidelines and the update is to lead to new affordable housing units. Even if tomorrow Illinois moved to push communities to submit plans, it would take years for the actual housing to be planned and built. According to various groups, there at least tens of thousands of affordable housing units needed in the Chicago region. If these legislative changes make a sizable dent in this number, this could help a lot of people.