Maine Gov. Janet Mills on Wednesday vetoed a bill designed to limit development of transmission lines that would deliver electricity out of the state.

“The bill (LD 170) would create inappropriate barriers to the development of transmission lines, which could hinder the ability of the state and region to meet our critically important climate and energy goals,” Mills said in a veto letter.

As passed with a committee amendment, the bill sets guidelines for regulatory approval of transmission lines that are deemed “nonessential,” in that they are not needed primarily for in-state electric reliability, in-state retail electric service or meeting Maine’s climate goals.

“LD 170 does not prevent future transmission lines in Maine to serve Massachusetts and others in the region,” Rep. Seth Berry (D), House chair of the joint Energy, Utilities and Technology (EUT) Committee, said in a statement. “On the contrary, it asks that they be developed for mutual benefit and in consultation with communities and landowners who may otherwise be forced to host new infrastructure.”

Designating transmission lines as nonessential based on their functional benefit outside of Maine misrepresents the regional nature of the New England power grid and the global nature of the climate crisis, according to Mills. For Maine and other states in New England to meet their climate goals, “it will be essential to work strategically on a regional level, and this bill would seriously interfere with those efforts,” she said.

Amendments made by the EUT Committee established nonessential line approval requirements that Mills called “vague, ill-considered and unworkable.” The requirements included ensuring the developer demonstrates it has negotiated with stakeholders, attempted to work with impacted communities and negotiated for shared ownership if the developer cannot finance the project through revenue bonds.

The bill also would direct regulators to consult with municipal governments affected by the potential taking of land by eminent domain for a proposed transmission line before approving it.

“I worked hard to address concerns that the public flagged in the [New England Clean Energy Connect (NECEC)] debate so that we have a more transparent and accountable process moving forward and that our clean energy transition proceeds at the necessary pace to meet our climate goals,” the bill’s sponsor, Rep. Nicole Grohoski (D), said in a statement.

Mills has been a steadfast proponent of the NECEC project, which is planned to deliver Canadian hydropower to the New England grid via a 145-mile transmission line that would run through Maine. Voters in the state, however, approved a measure in November to halt construction of the project.

Avangrid subsidiary Central Maine Power, developer of the project, agreed to stop constructing NECEC while the courts consider its claim that the referendum is unconstitutional.

Legislators will return May 9 to consider LD 170 and other vetoed bills. Mills urged the legislature to sustain her veto.

Grohoski said she is “surprised and disappointed” by Mills’ veto and hoped her colleagues will join her in voting to override it.