William Reilly led the Environmental Protection Agency in the George H.W. Bush administration.

As a former Environmental Protection Agency administrator, I thought I was familiar with all the twists and turns of the environmental review process.

I was wrong.

In Maine, a dispute over an electrical transmission line is raising the prospect of rewriting the government rules that allowed the project to go ahead — after those rules were fairly and legally applied. This effort to retroactively apply the revamped regulations could kill an important initiative, and, worse, if the gambit succeeds, it would set a terrible precedent nationwide.

Over the past seven years, backers of New England Clean Energy Connect (NECEC), which would bring inexpensive, clean, reliable power from Canada through Maine to the New England power grid, have secured the federal, state and local permits and approvals they need to build the project, two-thirds of which is in an existing transmission line corridor. (There is pending litigation about whether an additional approval is needed for a lease for about one mile of the line.) Experts who have reviewed the project said it will cut greenhouse gas emissions by about 3.5 million metric tons per year, the equivalent of taking roughly 700,000 cars off the road every year.

During this lengthy process, Avangrid, the company building the line, and its subsidiary Central Maine Power have made changes to reduce the transmission line’s environmental impact, including agreeing to limit clear-cutting, establish no-disturbance areas near streams and preserve in perpetuity 40,000 acres of Maine forest land.

The utility providing power to the line, Hydro-Québec, also has entered into an agreement with the Maine governor’s office to offer discounted electricity for Mainers, which is particularly important to Maine families who are struggling with high energy costs. Construction is underway, putting hundreds of Maine residents to work right away at good, paying jobs, and agreements have been inked for the NECEC to pay millions to Maine conservation funds.

But now, opponents of the project — including some environmental groups but also companies in the fossil fuel business — want to change the rules and halt the project.

They have gathered enough signatures to put a referendum on the Maine ballot in November; if the referendum passes, it would ban the transmission line, handing victory to the opponents who lost previously before all the state and federal agencies that reviewed the project.

And the referendum doesn’t stop there — it also says that, for future major transmission lines, the state legislature, and not the trained expert agencies, would decide whether they get approved.

If this tactic succeeds, it sets a terrible precedent. At both the federal and state levels, we have rigorous environmental review processes to ensure that decisions about infrastructure projects are based on science, data and public participation. And those decisions are typically made by agency officials with the technical expertise to evaluate evidence. As a further safeguard, their decisions are subject to review by independent judges, who are required to ensure that agency decisions are supported by the evidence and the law.

Sometimes that review process results in rejecting a proposal; though the proponents may not like that outcome, it is a risk they take. But the converse is also true, or at least it should be — projects that survive the gantlet of environmental review should not be subject to a second line of attack in which the rules get changed after the fact.

What is the point of environmental review if the outcome can be negated through a referendum? If this gambit in Maine succeeds, watch for it to be emulated elsewhere, with similarly damaging consequences.