A Superior Court judge has allowed a lawsuit against the state to proceed on grounds that conditions at troubled Bridgewater State Hospital may violate the federal Americans with Disabilities Act, a ruling that underscores the controversial use of seclusion and restraints at the facility.

The lawsuit, filed by the families of three former Bridgewater patients, claims that officials discriminate against the most severely mentally ill men in the state by consigning them to a facility run by the Department of Correction rather than one administered by the Department of Mental Health, where trained clinicians maintain policies designed to restrict the use of seclusion and restraints and provide higher-quality mental health care.

Attorney General Maura Healey had argued that the lawsuit should be dismissed because it does not claim that mental health patients held at Bridgewater are denied benefits available to persons who are not mentally ill — the traditional means of proving discrimination under the Disabilities Act — and because they are not treated “any differently from similarly situated inmates who are not mentally disabled.”

But Suffolk Superior Judge Paul D. Wilson ruled that the comparison between treatment of mental health patients held at Bridgewater and those treated at Department of Mental Health facilities is valid. He based his ruling on claims that staffers at DMH facilities “receive ongoing training in methods to avoid using seclusion and restraint, whereas the Bridgewater correctional officers who often make the seclusion and restraint decisions do not.”

In his May 12 ruling, Wilson also wrote that he was persuaded by assertions that DMH facilities provide more comprehensive mental health care, including “personalized treatment plans, exercise programs and other activities, and regular therapy sessions with licensed mental health professionals.”

Despite its name, Bridgewater State Hospital is a medium security prison, not a hospital. And the majority of its patients have never been convicted of a crime, though all have been charged. Some have been found not guilty by reason of insanity.

But many others have been committed after being found incompetent to stand trial or determined not responsible for their actions. In many cases, they were charged with minor infractions.

Roderick MacLeish Jr., the attorney representing the Bridgewater families, said the goal of the lawsuit is to compel the Legislature and Governor Charlie Baker to address longstanding problems at Bridgewater, either by moving all of the patients who have not been convicted of a crime to a new, separate facility, or by assigning administration of the Bridgewater prison to the Department of Mental Health.

“We’re hoping the suit will open the way for the Legislature and the executive branch to make the changes necessary to eliminate violations of federal law,” MacLeish said. “This ruling gives hope to everyone who because of a mental illness is locked up in a prison.”

Two years ago, the Globe reported that patients in Bridgewater’s Intensive Treatment Unit were placed in restraints — their wrists and ankles strapped to a bed — or held in seclusion at more than 100 times the rate of patients at other state mental health facilities.

The Globe also reported that from 2009 through 2013, three Bridgewater patients, including 23-year-old Joshua Messier, died from causes attributed to the use of four-point restraints.

Last month, Leo Marino , a 43-year-old father of two with a history of mental illness and suicide attempts, choked to death while being held in seclusion in the unit, raising questions about the manner of his death and whether he was adequately monitored by Bridgewater staff. After the death, the State Police said they would investigate.

In his ruling, Wilson also refused to dismiss a portion of the lawsuit that claims former Department of Correction commissioner Luis S. Spencer and former Bridgewater superintendent Robert Murphy knew about the excessive use of seclusion and restraints at Bridgewater and deliberately allowed subordinates to continue using those tactics, in violation of patients’ rights.

“It is a fair inference that facility superintendent Murphy, working every day at a facility housing many mentally ill persons being subjected to the extraordinarily high rates of restraint and seclusion . . . must have been aware of these rates,” Wilson wrote, adding that “these facts plausibly suggest that Spencer’s conduct also amounted to deliberate indifference.”

‘This ruling gives hope to everyone who because of a mental illness is locked up in a prison.’

After disclosures about Messier’s death, Governor Deval Patrick formally reprimanded Murphy and Spencer for failing to follow regulations.

Spencer was forced to resign after administration officials said he delayed an internal investigation into a separate violent incident involving another patient and a guard.

MacLeish said he believes Wilson’s decision to allow the claims against Spencer and Murphy will deter correction department officials from failing to follow through on their legal obligations to protect Bridgewater patients from the illegal use of seclusion and restraints, which are supposed to be used only in emergencies when a patient has been violent or has threatened violence.

“Perhaps now state officials will see that ignoring state law on the use of seclusion and restraints can result in legal action for which they can be personally liable,” he said.

A spokeswoman for Healey’s office referred questions to the Department of Correction, which said it maintains a policy of not commenting on ongoing litigation.

But MacLeish said he is hoping to dissuade Healey from appealing Wilson’s ruling. “This is an attorney general who is supposed to represent all the people in the state, including the patients at Bridgewater State Hospital,” he said.