As a 376-foot-long unpowered barge nosed its way into Buzzards Bay, the first mate of the tugboat pulling the vessel left the helm and missed a radio warning from a nearby mariner that he was straying off course.

The barge struck a rocky outcropping that ripped a 12-foot-by-2-foot gash in its hull. Almost 100,000 gallons of oil belched into the bay, an environmental disaster that killed hundreds of birds, polluted 93 miles of coastline, and forced thousands of acres of shellfish beds to shut down.

After the 2003 spill, the state passed a law mandating every unpowered barge transporting oil through Buzzards Bay be escorted by a second tugboat — in addition to the one moving it — to help prevent another incident. But the shipping industry has fought the requirement for years and recently filed a suit meant to invalidate the law.


Now, Attorney General Maura Healey is fighting back, petitioning a federal court to let Massachusetts intervene in the suit.

“Buzzards Bay is a treasured resource that must be protected,” Healey said in a statement. “Requiring an oil tank barge to use a tugboat escort is a common-sense and cost effective way to prevent catastrophic oil spills in our waters, and we are deeply disappointed that the shipping industry is once again suing to overturn this important and longstanding law.”

The American Waterways Operators, which represents the tugboat, towboat, and barge industry, filed the lawsuit last year against the US Coast Guard, part of a series of legal challenges that began in 2005 against the tugboat requirement.

The group argues that the Massachusetts tugboat law is unconstitutional because it encroaches on federal jurisdiction over interstate commerce, an area that the US Constitution reserves for the federal government, not individual states.

And the industry says a broader issue at stake here is whether its members, which transit the waters of many states, have to grapple with a hodgepodge of different requirements in each one.


“Maritime commerce is a major driving force behind the American economy, with commercial mariners routinely crossing state lines to deliver to communities across the country,” said Ben Lerner, a spokesman for the group. “These mariners are engaged in interstate commerce, and they need regulatory consistency from one state to the next so they can efficiently deliver their cargoes without having to disrupt navigation to contend with a patchwork of overlapping or conflicting state regulations.”

The industry group accuses the Coast Guard of dragging its feet on making regulations related to the tugboat requirement, preventing the courts from issuing a final ruling on its constitutionality.

The tugboat law has been in effect continuously since 2011. Several other provisions of the original statute — the Massachusetts Oil Spill Prevention Act — have been struck down by the federal courts as unconstitutional.

The Coast Guard, for its part, indicated in court filings that it has no beef with the tugboat requirement and has the right to let it stand.

It noted it had successfully sued Massachusetts over several other provisions of the law put in place after the oil spill, including a state mandate on alcohol and drug testing and mandatory vessel routes.

“The sole outstanding issue — whether [oil] barges need tug escorts in Buzzards Bay — concerns an area where the Coast Guard is allowed to change its policies,” the agency wrote in a May court brief.


The Coast Guard said the trade group “brings this rearguard action to foreclose the potential for any policy change.”

It said the group’s only stake in the fight “is the economic interest some of its members have against paying” tug escort costs, even though the group represents tugboat and oil barge companies alike.

In its filings, the agency noted that as part of a formal assessment of Buzzards Bay in recent years, it had solicited the opinions of members of the tug and barge industry, the commercial vessel industry, the commercial fishing industry, environmental organizations, law enforcement, local municipalities, and tribal groups.

One of the most common recommendations was having the federal government support the tugboat escorts “as an additional risk mitigation strategy to better balance the risks of petroleum discharge and environmental damage.”

A Coast Guard spokesman declined to comment on the pending legal matter.

In a statement, Lerner, of the American Waterways Operators, said the group and its member companies are committed to operating at the highest safety and environmental standards.

“But those high environmental standards should be rooted in a nationally consistent framework overseen by the federal government — as the US Constitution requires with respect to interstate commerce — rather than by the individual states,” he said.

A judge could issue a ruling on motions for summary judgment in the lawsuit this year.

Joshua Miller can be reached at joshua.miller@globe.com.