Hopewell Township’s planning board voted in December to amend the township master plan to allow housing to be built on the east side of Scotch Road

The state Supreme Court ruled on Jan. 18 that municipalities must account for affordable housing not built between 1999 and 2015, but the ruling only set the stage for the next round of negotiations on the contentious issue.

Now five towns in Mercer County, including Hopewell, are involved in a trial in Mercer County Superior Court, the outcome of which may finally determine how many units of low- and moderate-priced housing they will be required by the state to zone for.

Hopewell, Lawrence, Princeton, East Windsor, and West Windsor are before Judge Mary Jacobson this month as the state makes yet another attempt to reconcile local zoning laws with its so-called Mount Laurel doctrine, the landmark 1980’s court decision that mandated that municipalities must build their fair share of affordable housing.

The Supreme Court ruling means that towns will be expected to allow for the development of affordable housing that was not built during the 16 years the state’s Council on Affordable Housing was unable to come up with any clear methodology for determining how many units towns should have to provide for. Failure to do so could open towns up to “builder’s remedy” lawsuits, by which developers can appeal to the courts to override local zoning laws that restrict the construction of affordable units.

The Supreme Court effectively disbanded COAH in 2015, putting affordable housing in judiciary hands. While towns will now be expected to account for the ‘gap period,” the ruling did not provide any figures or prescribe any formulas for figuring out how many units would be needed.

The Fair Share Housing Center, a Cherry Hill-based nonprofit that has been given the power by the courts to negotiate with or sue municipalities that haven’t met their Mount Laurel obligations, hailed the ruling as a “victory for tens of thousands of New Jersey families.”

“This decision clears away one of the main obstacles remaining in the fight for fair housing in New Jersey,” said Kevin Walsh, executive director of the FSHC, in a statement. “The towns who were fighting in court are outside the mainstream and now know that they will not be rewarded for further obstruction and delay.”

The FSHC says approximately 90 municipalities have reached agreements to fulfill obligations of more than 32,000 homes since the Supreme Court turned enforcement of the state’s fair housing laws over to the trial courts in 2015. Hamilton and Ewing have settled, and Dave Fried, the mayor of Robbinsville, has said that Robbinsville has also settled, pending Jacobson’s acceptance of a tentative agreement between Robbinsville and the FSHC.

Hopewell Township’s planning board voted in December to amend the township master plan to allow housing to be built on the east side of Scotch Road, near the Capital Health Medical Center. The next step is for the township committee to draft a detailed ordinance to be sent back to the planning board.

Housing built on the site could be used to help Hopewell meet its affordable housing obligation, once that is known. The land east of Scotch Road has sewerage capacity, which cannot be said for most of the developable land in Hopewell. Areas without sewers are unsuitable for the development of affordable housing.

Planning board chair Karen Murphy told the Express last month that the master plan change needed to be made to show the state that the township was serious about accepting its fair share. She also expressed frustration with the affordable housing process, saying that whatever number the state comes up with should be in keeping with historical growth rates in the township.

FSHC said the trial before Judge Jacobson is important because it is expected to be the first countywide fair housing trial that does not end in a settlement. It argues that several Mercer County towns have among the highest fair housing obligations in the state.

FSHC has said that the Supreme Court ruling paves the way for more than 200,000 affordable units to be built throughout the state. But Michael Cerra, assistant executive director of the state League of Municipalities, told philly.com the courts were unlikely to embrace such a large number.

Editor’s Note: An earlier version of this story listed six towns in the litigation trial. Robbinsville has settled. We regret the error, and we have updated the story to reflect the changes.