“This important step will give local leaders the tools they need to provide all Americans with access to safe, affordable housing in communities that are rich with opportunity,” said HUD Secretary Julian Castro.

Parts of the new rule will take effect in 30 days.

By law, communities are expected to affirmatively further fair housing through the way they use federal funds, including Community Development Block Grants (used for a variety of development initiatives), public-housing-authority programs such as Housing Choice Vouchers and housing complexes, and HOME grants, which fund the development of affordable housing.

But the law previously only required that, to get these funds, communities certify that they have a document called an Analysis of Impediments outlining why people could not find affordable housing, and that they are taking actions to overcome these impediments. Many communities don’t update their Analysis of Impediments, though; a 2010 GAO report found that some grant recipients didn’t have a document at all, and in other communities, the reports were from the 1990s.

The new rule replaces this process with a tool that allows participants to assess fair housing issues in their communities with the aid of data provided by HUD. Cities, regions, or housing authorities will submit a document called an Assessment of Fair Housing to HUD, which will review and accept the document. That document will analyze integration patterns and disparities in access to high-quality affordable housing, and will include input from the community on what to do about it. HUD can choose to reject parts of a community’s Assessment of Fair Housing if it determines that that plan is incomplete or is inconsistent with fair-housing laws.

This may all just sound like a change in the way housing authorities do their paperwork, but for housing advocates, this is a big deal.

“This is going to be an incredibly important and positive step to changing things over the long run,” said Ed Gramlich, a special advisor to the National Low Income Housing Coalition.

Previously, there had been no definition of what, exactly, an impediment to fair housing is, and what communities should do about it. The county of Westchester, in New York, for example, took millions of dollars of federal housing money and claimed to comply with fair-housing mandates. It signed a consent decree in 2009 to settle a lawsuit about this, but still has not taken any steps to comply with fair-housing laws, and the county executive there has spoken publicly about his opposition to integration.

Now, HUD will be hopefully able to spot such misuses of funds before the money is spent. Jurisdictions have guidance for how they can “affirmatively further fair housing,” and administrations that want to enforce the Fair Housing Act have more tools at their disposal.