A Cambridge transgender woman, outraged that convicted wife killer Michelle Kosilek could receive a free gender reassignment operation that health insurers refuse to cover for law-abiding citizens, has filed suit demanding the same right to tax-funded surgery — a move critics say could mark the beginning of a dramatic, costly shift in entitlements under the controversial federal court ruling.

Anita T. Phoenix, 59, filed a federal lawsuit earlier this month claiming that Medicare and MassHealth discriminated against her.

“How can a convicted murderer get this done for nothing?” said Phoenix, who filed the suit without an attorney. “I have the same problems, and I have to pay for everything even though my therapist and an independent psychiatrist says it’s medically necessary. A convicted murderer has better health coverage than I do.”

State Sen. Bruce Tarr (R-Gloucester), who has supported the Department of Correction in the Kosilek fight, said the lawsuit shows the dangers of the controversial case.

“It will open the door not only to other law-abiding people to make that claim, but people who are incarcerated to seek other forms of surgery that they wouldn’t otherwise obtain,” said Tarr. “What we’re talking about here are extraordinary measures that most citizens can’t afford and wouldn’t undertake. If we set a precedent in allowing Kosilek to obtain this kind of surgery, what we’d essentially be doing is opening the door for all different types of surgeries that are extraordinary to become the subject of entitlement.”

In 2012, federal Judge Mark Wolf ruled the state must pay for Kosilek’s surgery. DOC is making preparations for the operation should a pending appeal fail.

Phoenix said she struggled with suicidal thoughts for years before being diagnosed with gender identity disorder. She said she went bankrupt paying for her 2008 surgery, which MassHealth wouldn’t cover, and now needs corrective surgery, which Medicare doesn’t pay for.

“It’s not just me,” said Phoenix. “Other transgender people are in this same boat and need this surgery but can’t afford it.”

Officials at Medicare and MassHealth did not return calls seeking comment.

The Kosilek case sets a precedent under the 14th Amendment, which protects against the government denying fundamental rights, said Boston University law professor Tracey Maclin.

“It certainly provides support for their legal position,” said Maclin. “As long as it’s on the books and until the precedent is overturned, it’s the law.”

But Timothy M. Burke, a civil discrimination lawyer, said there’s a higher obligation to provide care for inmates: “It provides some precedent value, but I’m not sure it’s going to be conclusive in demonstrating there is need to provide the coverage. But it’s a new arena.”

Vermont, Connecticut, California, Oregon, Colorado and Washington, D.C., already bar private insurers from denying coverage for the surgery. And in December, federal officials decided to revisit their coverage of gender-transition surgery, which is based on 1981 research, said Suffolk University law professor Renee Landers.

“It does seem that medicine has advanced since 1981, and with two major medical groups supporting the procedure — the American Medical Association and the American Psychological Association — it’s likely the policy could change,” said Landers. “The lawsuit does have the affect of putting some pressure on the agency.”

Tarr said, “This lawsuit is totally predictable by a member of the public about the outrageous nature of providing a murderer with gender reassignment surgery. What’s also predictable, if this lawsuit were to be successful, and if Kosilek is successful, then the door is going to be forced open to not only this type of surgery, but other things that many would consider to be elective or not medically necessary, to be the subject of taxpayer funding.

“I would suggest there is almost a limitless number of possibilities as to what folks might argue is medically necessary,” Tarr said.

Donna Goodison contributed.