The New Jersey Superior Court Appellate Division will hear arguments June 6 on whether municipalities have an obligation to zone for affordable-housing units that they did not allow between 1999 and 2015.

A panel of judges is scheduled to convene that day at the Old Courthouse in Mount Holly, built in 1794 and modeled on Congress Hall in Philadelphia.

A ruling could affect by tens of thousands the number of affordable-housing units the state's 565 municipalities must zone for in the decade ahead under the state Supreme Court's Mount Laurel rulings.

Between 1999 and 2015, the state Council on Affordable Housing (COAH) failed to devise an acceptable formula for calculating municipalities' obligations under the Fair Housing Act, and few units were created.

Advocates for affordable housing assert that the state's failure to devise a formula during those years, known as the "gap period," did not erase municipalities' obligations.

The Fair Share Housing Center, which has intervenor status in ongoing litigation, contends that municipalities statewide must build about 202,000 units by 2025 to meet their Mount Laurel obligations. Fair Share says about half of those remain from the gap period.

But a coalition representing half the state's cities and townships contends that municipalities have zero affordable housing obligations for the gap period, and just 37,000 new ones by 2025.

That coalition, represented by Brielle attorney Jeffrey R. Surenian, argued in a May 13 brief that the "plain intent" of the 1985 Fair Housing Act was to create "reasonable" fair-share obligations, "not to overwhelm municipalities with the patently unachievable burdens currently advanced by developers and nonprofit organizations."

Surenian said Monday that he had felt confident that the Appellate Division would accept his appeal "because I thought we had an important point to make."

"If the public understood the millions of dollars that Fair Share Housing is costing the state because of its patently unrealistic position, they would want this decided now," he said.

Since 1975, the Supreme Court has held that towns may not adopt zoning regulations that exclude low- and middle-income households, and in 1985 the legislature adopted the Fair Housing Act to implement those rulings.

Kevin Walsh, Fair Share's executive director and one of its attorneys, said Monday he was surprised the court accepted Surenian's appeal because COAH and the Supreme Court had both ruled that "just because some towns did the wrong thing doesn't mean they get a pass."

Overseeing Mount Laurel-type housing issues fell to Superior Court in March 2015, when the Supreme Court declared that COAH, which was charged with implementing the Fair Housing Act, had grown "moribund." It directed all municipalities to develop new fair-housing plans and submit them to their relevant Superior Court for review and certification.

The question of whether municipalities have gap-period obligations came to a head in February, when Superior Court Judge Mark A. Troncone in Toms River ruled in a case involving Barnegat Township, Ocean County, that "municipalities are constitutionally mandated to address this obligation."

"The court is satisfied there exists a rational methodology to calculate and determine the affordable housing need which arose the during the 'gap period' between 1999 and 2015," Troncone wrote.

Troncone's opinion had been much anticipated by other judges hearing affordable housing cases around the state, and was viewed as influential.

Surenian, who was representing Barnegat before Troncone, appealed the ruling to the Appellate Division in early March. The Supreme Court, in an unusual move, directed the appeals court to schedule a hearing by the end of June.

In his brief, Surenian wrote that "resolution of this gap issue is essential to establishing the basic parameters of a plan, since the gap obligation could represent 40 to 60 percent of [a] municipality's . . . obligation" between now and 2025.

Walsh said he was confident that the appeals court, and the Supreme Court if it decided to hear the issue, would find that towns must meet gap obligations.

"All this time, housing in New Jersey has become less affordable because towns were blocking legitimate development," he said. "This means kids and families are being kept out of good school districts, and people are living farther from their jobs.

"Some towns have been proceeding reasonably," he said, "while others have virtually nothing to show for 16 years."