The U.S. Supreme Court will meet today to decide whether they will grant or deny review to a set of cases that challenge the so-called Defense of Marriage Act. Should the Court oblige, the hearing would pose the most serious challenge to the law’s constitutionality since its passage in 1996.

The Defense of Marriage Act is a discriminatory law that, for the purposes of the federal government, defines marriage as the union between one man and one woman. As a result, even though same-sex marriage is legal in nine states and the District of Columbia, the Defense of Marriage Act prevents the government from recognizing those marriages as legally valid. In doing so, the law restricts who can be counted as family in several aspects of federal policy.

This unfair treatment is why lower courts have consistently found the Defense of Marriage Act unconstitutional. The Supreme Court now has the historic opportunity to weigh in and affirm that discrimination and unequal treatment under the law do not comport with our nation’s constitutional values. As the High Court convenes today, it is more important than ever to remember what’s at stake for families headed by same-sex couples and, just as importantly, their children.

By prohibiting the federal government from recognizing the legally valid marriages of same-sex couples, the Defense of Marriage Act deprives these Americans from far more than just the institution of marriage. The law also denies same-sex couples and their children equal access to key government programs and tax credits that are otherwise afforded to different-sex couples. In doing so, the law poses a direct threat to the health, well-being, and economic livelihood of families headed by same-sex couples.

Here are five other ways the Defense of Marriage Act negatively impacts same-sex couples and their children.

1. The Defense of Marriage Act contributes to economic insecurity among families headed by same-sex couples

The Defense of Marriage Act imposes significant financial burdens on families headed by same-sex couples. Same-sex spouses cannot file joint tax returns, for example, which often means they pay higher taxes compared to married heterosexual couples. In some cases, parents cannot claim tax credits and deductions, including those for child care or education expenses. Gay workers must even pay an average tax of $1,069 per year on health insurance for their spouse or partner because of the Defense of Marriage Act.* The bottom line: Families headed by same-sex couples can pay thousands of dollars more in taxes than a family led by different-sex spouses.

What’s more, these financial disparities under the Defense of Marriage Act worsen existing economic disparities and employment hardships facing families headed by same-sex couples. Contrary to common stereotypes, these families make $15,500 less per year than families headed by different-sex couples, contributing to the fact that children of same-sex couples are twice as likely to live in poverty as children being raised by heterosexual parents.

2. The Defense of Marriage Act compromises the health of families headed by same-sex couples

Same-sex couples and their children can be denied health insurance coverage because of the Defense of Marriage Act. For public-sector employees working for the federal government—the nation’s largest employer—health insurance is denied to same-sex spouses—and often their children, as well—because of the law. Private-sector employees often fare no better. Since regulation of employee benefits falls under federal law, and federal law does not recognize the legally valid marriages of two men or two women, many private-sector employers are within their rights to deny benefits such as health insurance to a same-sex spouse or their child, even if marriage equality is legally recognized in the state in which they operate.

These gaps in coverage impose both physical and financial harm on families headed by same-sex couples. Lack of health insurance contributes to the negative health outcomes and disparities facing the gay population. And when employees cannot enroll family members in an employer-sponsored plan, they face the difficult choice between obtaining costly health insurance plans in the private market or forgoing health insurance coverage altogether.

3. The Defense of Marriage Act threatens the security of our senior citizens

The Defense of Marriage Act is especially burdensome for elderly gay Americans who, similar to their straight counterparts, have paid into Social Security for generations to ensure their financial security in their golden years. When two people are married and collecting Social Security, the lower-earning spouse may increase his or her benefit by up to 50 percent of the higher-earner’s benefit. Additionally, if one spouse dies, the surviving spouse receives a one-time death benefit. When one spouse dies, the other is also exempt from various estate taxes when the surviving spouse receives a deceased spouse’s inheritance.

But because same-sex couples are not “spouses” in the eyes of the federal government, elderly same-sex couples are not afforded these kinds of economic safeguards and financial security benefits that ensure our elders have the opportunity to grow old with dignity. One of the cases the Supreme Court may decide to hear, for example, concerns Edith Windsor, an 83-year-old woman who was required to pay more than $363,000 in federal estate taxes upon inheriting the home of her deceased female partner of 40 years. Had the federal government recognized her marriage—as it does for different-sex spouses—Edith would not have been required to pay any tax on that inheritance.

4. The Defense of Marriage Act divides binational families

Under federal immigration law, heterosexual Americans can sponsor their spouses for residency in the United States. Unfortunately, the Defense of Marriage Act denies same-sex binational spouses these family reunification rights. As of 2010 there were an estimated 28,574 binational same-sex couples in America, and nearly one-third of those couples were raising children. Though the Department of Homeland Security announced earlier this year that long-term same-sex partnerships must be considered when handling deportation cases, nothing short of full marriage recognition can guarantee these couples and their families will not be pulled apart.

5. The Defense of Marriage Act disrespects our military members and their families

Following the repeal of “Don’t Ask, Don’t Tell,” gay service members may serve openly, but their families remain second-class citizens. Although the Pentagon is working to include same-sex spouses in the benefits programs that do not rely on a federal definition of marriage, the most robust services—aimed at providing financial security to service members and their families—fall squarely within the jurisdiction of the Defense of Marriage Act.

In other words, crucial benefits such as military health insurance, increased base and housing allowances, relocation assistance, and surviving spouse benefits are not offered to the same-sex spouse of a service member, regardless of whether the couple was married in a state that recognizes their marriage. Until the Defense of Marriage Act is repealed, military families headed by same-sex couples will continue to be denied the benefits they have earned and the respect they deserve for serving our country.

The Defense of Marriage Act is patently unconstitutional

We can measure the impact of the Defense of Marriage Act by the number of couples affected or extra dollars paid, but the most destructive elements are unquantifiable. The Defense of Marriage Act means the children of gay parents bear the brunt of an unjust law. The Defense of Marriage Act adds another burden to the backs of our men and women in uniform, who already sacrifice so much. The law symbolizes a government that has failed to keep up with the changing reality in this country—that gay couples and their children are part of the American fabric.

Fair-minded policymakers are working to put an end to the Defense of Marriage Act, but the prospect of repeal under the 113th Congress appears bleak, given the conservative and antigay makeup of the House of Representatives. In the near term, the best prospects for repeal now lie with the Supreme Court, which today will decide whether to grant or deny review to this patently unconstitutional law.

It’s time to stop this government practice that serves no other purpose than to create two classes of families and deprive gay Americans of the resources they need to ensure the prosperity of their spouses and children. The Defense of Marriage Act is an assault to our core values, which hold that all people, as well as their loved ones, are equal under the law. Equality cannot wait.

Katie Miller is a Special Assistant and Crosby Burns is a Research Associate for the LGBT Research and Communications Project at the Center for American Progress.

* In this column, “gay” is used as an umbrella term to describe people that identify as lesbian, gay, or bisexual.