DID THE controversial MBTA Communities housing law force towns to shell out money to devise carefully crafted multifamily zoning plans, or were any expenditures a voluntary choice that municipalities made to navigate thorny local politics?

Justices on the state’s highest court are wrestling with that question in a lawsuit brought by the town of Marshfield. After a lower court last year shot down arguments from a group of municipalities that they should not be forced to comply with the 2021 law requiring multifamily zoning near MBTA service, because it was an “unfunded mandate,” the South Shore town appealed, and the Supreme Judicial Court agreed to hear its case.

What the SJC will decide may turn on a simple, pointed line of inquiry.

“What were the expenses?” Justice Dalila Wendlandt asked Marshfield’s attorney, Robert Galvin, during oral arguments on Wednesday. “You’re saying it’s an unfunded mandate, and I’m wondering what the funds are that the town of Marshfield claims it was required to expend in order to comply with a state law that just requires ‘one district of reasonable size in which multi-family housing is permitted as of right.’”

Galvin offered up no line-item cost, and the town had not laid out specific expense in its initial compliant. But Marshfield was forced to employ a person to develop zoning modeling, Galvin told the court, and the town “incurred expense associated with” navigating the 22 pages of compliance regulations.

State law bars legislators from creating a direct financial burden on municipalities without providing a source of funding. Courts have found that there is an exception, however, for “incidental local administration expenses” that come along with abiding by a law.

“Our cases say that forcing you to make difficult choices is not a mandate,” Justice Scott Kafker said to Galvin. “That’s where I lose you. Modeling may have been expensive, but you made a choice to try to accomplish that statute that way as opposed to another.”

Attorney General Andrea Campbell’s office argues that the MBTA Communities law does not actually create a significant cost obligation. If Marshfield wanted to, it could have come into compliance by passing a simple line saying that multifamily zoning was allowed in every district of the town, said Esme Caramello with the attorney general’s office.

The regulations are not so complicated that complying requires more than incidental expense, Caramello said. The law allows for municipalities to bring other policy preferences into their process, but it does not require an “elaborate” process to get into compliance, she said.

Housing, economic development, and real estate groups submitted briefs in support of the state, arguing that “if MBTA Communities do anything more than ordinary planning tasks tailored to achieving technical compliance — like paying to develop complex and bespoke zoning districts — the associated costs would be voluntary and not covered by the local mandates law.”

If Marshfield had approved a plan to just rezone the whole town, Galvin acknowledged, the costs to the town would have been “nominal.” But the “extraordinary expense” came from developing a plan that accommodated local preference and the reality that not all land in the town would be possible to develop.

Justices seemed to agree that rezoning is not necessarily a straightforward project.

“A lot of communities where there is local opposition – or you just have to find the right place to have this district – it’s not as easy as ‘we’re gonna put it here or put it there,’” Justice Serge Georges, Jr. said. To be flexible and creative in responding to community preferences, he said, is going to be “more than what local zoning officials just do.”

Whether the rezoning involves incidental expenditures or something more, getting most of the MBTA Communities into compliance did require local money and effort. Gov. Maura Healey has rolled out a grant program to “reward” compliant communities, and the state housing office regularly touts state and nonprofit staff hours and funding dedicated to assist with coming into compliance.

The ongoing fight over the transit-centered housing law has played out in the middle of a serious housing crunch. The state has said 222,000 new homes need to be built by 2035 to meet pent up demand.

The Healey administration says that through policies like the MBTA Communities law and streamlining environmental review processes, the state is poised to “beat” that goal.

Recent data indicate a bumpy ride, even if the state does ultimately manage to hit the housing mark. Tracking from the Metropolitan Area Planning Council released Wednesday afternoon found that Metro Boston – which includes several of the major MBTA Communities – posted very sluggish permitting activity in 2024.

Meanwhile, some smaller municipalities remain vehemently opposed to the rezoning process, prompting Campbell to bring suit against nine recalcitrant towns in late January.

After Campbell’s lawsuit was announced, Holden’s town manager, Peter Lukes, suggested the move was irrelevant to the Worcester County community because the town was scheduled to vote within days on a plan that would bring it into compliance with the MBTA Communities law.

But earlier this week town meeting members rejected the rezoning plan by a 2-to-1 margin, leaving Holden squarely in the attorney general’s crosshairs.

“At this point, it really doesn’t look like something would pass no matter how appealing it might be to some, or how much we think it would be effective,” Lukes told GBH News after the vote.

Getting a reprieve from the high court is one of the few routes left for reluctant towns.

Superior Court Judge Mark Gildea concluded last June that the municipalities claiming “unfunded mandate” were mostly leaning on speculative future infrastructure costs and did not provide facts to support an argument that the towns were so unique that costs of designating complaint districts required dedicated state funding. Without those specific facts, Gildea dismissed the suit.

Supreme Judicial Court justices split their time on Wednesday probing whether the MBTA Communities law created a direct expense in the text of the statute itself, or whether Marshfield’s case might just be dead in the water because the town did not claim direct costs clearly imposed by the law in its initial complaint.

Even if the suit isn’t ruled procedurally out of order, the justices seemed skeptical of the idea that the law places an undue financial burden on communities.

The cost of choosing how to comply seems to fit inside “classic incidental expense,” Kafker told Marshfield’s attorney. “The fact that you made it more expensive was a choice you made.”