While most Massachusetts communities have complied with the state's new multifamily zoning law, Attorney General Andrea Campbell issued a warning to those that haven't taken the required steps.

Campbell released an advisory Wednesday stating that the MBTA Communities zoning law is mandatory and any jurisdictions that don't meet its deadlines may face legal action from the state or outside advocacy groups, the Boston Globe first reported.

“While the housing crisis disproportionately affects communities of color and poor, working families, it threatens all of us along with our economy and thus requires all of us do our part including ensuring adequate development of affordable, transit-oriented housing for our residents and families,” Campbell said in the advisory.

The law, signed in 2021 by then-Gov. Charlie Baker, requires communities with MBTA transit stations to create multifamily zoning districts. The state's rules for implementing the law set a minimum number of units each community must allow, and in total they would add more than 280,000 units of development potential.

Campbell said the law "was enacted to remove barriers," and that any town or city that doesn't comply would be protecting a certain class of residents while pushing out others with lower incomes and people of color, effectively breaking fair housing laws.

The warning comes after four of the 177 cities and towns required to comply with the law failed to file preliminary proposals, including Holden and Middleborough, which have been vocal opponents of the law.

Many of the towns that have submitted their action plans may still face pushback from local officials and residents as zoning proposals reach town meetings and discussions.

Last month, Brookline saw its own debates about the proposed zoning changes it could make, with tension growing between those that want to preserve the status of the town and those that want to bring in more affordability.

Although there is significant pushback, towns and cities that have begun to work on zoning plans say that there is potential for a significant boost in economic development, the Boston Business Journal reported Wednesday.

The law's next major deadline isn't until the end of the year, when towns and cities that have stations on the T's Red, Orange, Blue and Green Lines will have to submit their zoning changes to the state.