WASHINGTON -- The U.S. Supreme Court’s decision on the constitutionality of the Defense of Marriage Act will have implications far beyond how much same-sex couples might owe in income and estate taxes.

Striking down the portion of the 1996 law that’s under challenge might affect more than 1,100 federal statutory provisions in which marital status is a factor.

The most crucial provisions are fairly obvious, such as laws that allow married couples to file federal income taxes jointly, inherit Social Security benefits, sponsor their spouses for visas or defer federal estate taxes on property passed on to surviving spouses.

These benefits are vitally important to married couples, said Bruce Bell, the legal information line manager for Gay & Lesbian Advocates & Defenders, a legal rights organization in Boston.

“They provide far more in the way of really major benefits than the states do, by and large,” Bell said.

Key federal laws also pay death benefits to spouses of public safety officers killed in the line of duty, allow married workers to take up to 12 weeks of leave to care for sick spouses and give eligible veterans the right to be buried next to their spouses in military cemeteries.

Married couples also may transfer money to each other without owing gift taxes. Federal employees or service members may share their retirement or health benefits with their spouses. Employees also may ensure that their spouses receive uninterrupted health care coverage between jobs.

Some of the rules and regulations that apply to married couples are more obscure, ranging from the calculation of mining claim maintenance fees to conflicts of interest in the certification of agricultural loans.

One of the strangest federal provisions tied to marital status is the Guano Islands Act of 1856, which allows U.S. citizens to take possession of islands that are covered in deposits of feces from bats, seabirds and seals. The excrement, known as guano, was highly prized as fertilizer.

Any American who discovered such an island could claim exclusive rights to collect the guano and sell it, as long as the island wasn’t occupied or in another country’s jurisdiction. The law says the discoverer’s widow may inherit rights to the island – and any pricy poop on it.

In some cases, being recognized by the federal government as married limits a person’s eligibility for a government loan or benefit.

For example, a student who’s applying for financial assistance for college using the federal aid form must list contributions from parents. Under current laws, if the student’s parents are a same-sex married couple, only one parent’s income and assets may be listed, potentially increasing the amount of aid that student may receive.

Supplemental Security Income, Medicaid and the Medicare prescription-drug benefit’s low-income subsidy program also are linked to a family’s income and assets, so some people might qualify for fewer benefits if the federal government started counting same-sex spouses’ resources.

“Sometimes you benefit, sometimes you lose, but this is a case where the government is losing, obviously,” Bell said.

In fact, the Congressional Budget Office reported in 2004 that federal recognition of marriages between same-sex couples nationwide would result in an increase of $1 billion per year in the federal budget’s bottom line through 2014.

But if the high court does decide to extend federal benefits to same-sex couples, the ruling will apply only to married same-sex couples in the District of Columbia and the nine states that permit gay marriage. For gay and lesbian couples in civil unions or domestic partnerships in states such as California, little will change unless same-sex marriage becomes legal where they live.

“They’re going to have to get to marriage before they get the benefits,” Bell said.

• Read more articles by Lindsay Wise

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