The state’s highest court has tentatively set an argument date in Central Maine Power owner Avangrid’s suit over the law restricting transmission development that voters approved last fall. 

The utility challenged the referendum as unconstitutional. A Superior Court judge late last year declined to issue an injunction that would have temporarily stopped the law from taking effect, then sent the case up to the state Supreme Judicial Court to weigh in on open legal questions.

CMP has since paused construction while the lawsuit is ongoing but argues it has a vested right to continue building the project and that the referendum is illegitimately retroactive. The utility hopes to complete the project, which would bring Canadian hydropower into New England, by 2023 in order to satisfy the terms of a deal to help meet Massachusetts’ climate change goals. 

In newly posted filings on the referendum case, prominent attorneys in the state weigh in with amicus briefs arguing in CMP’s favor, while competing energy company NextEra argues the high court should uphold the referendum, among other briefs from all sides of the issue. 

The oral argument on the matter is tentatively scheduled for when the high court sits in May. 

The court also has an appeal pending on a separate case related to the CMP corridor. In this case, a lower court judge found the state had erred in how it issued a public lands lease for the transmission line. The appeal of that decision may or may not be argued in May as well. 

It’s shaping up to be a busy month for the stalled transmission line, with state environmental regulators scheduled to hear appeals of past approvals of the project a week after the high court takes up the referendum case.