BOSTON (AP) – Some employers with federally regulated health plans have decided not to extend health benefits to spouses of gay and lesbian workers, saying the plans are not bound by Massachusetts’ same-sex marriage law.

General Dynamics Corp., FedEx Corp. and Caritas Christi Health Care are among the employers that do not provide married gay and lesbian workers in Massachusetts with the same health benefits available to heterosexual married couples.

“In determining the definition of dependent spouse, General Dynamics applies the spouse definition from the federal Defense of Marriage Act,” the Virginia-based defense contractor, which has 3,000 workers in Massachusetts, said in a statement to the Boston Globe.

The 1996 Defense of Marriage Act denied federal recognition of same-sex marriages by defining marriage as between a man and a woman.

The employers provide medical care through self-insured health plans in which the company – not an insurer – collects premiums and pays the medical bills of its workers.

Such self-insured plans, which are used to save money amid skyrocketing healthcare costs, are regulated by federal law.

Sharen Litwin, a Boston labor attorney, said companies with self-funded plans likely cannot be compelled to extend coverage to spouses of gay and lesbian workers.

Some employers that self-insure, however, extended coverage to spouses after May 17, when same-sex marriage became legal in Massachusetts. They include Gillette Co., National Grid USA and UniteHere, the union of garment and hotel workers.

Catholic institutions early this year began debating how to handle the issue because of their strong opposition to same-sex marriage.

“We have to be faithful to the teachings of the Catholic Church,” said Diana Franchitto, spokesperson for Caritas Christi, a Boston Archdiocese affiliate that oversees six hospitals.

But gay rights supporters argue that same-sex marriage opens the door to reinterpretation of a host of state and federal laws.

“There are some good legal reasons why we might be able to challenge [denial of benefits],” Michele Granda, attorney for Boston-based Gay & Lesbian Advocates & Defenders.