Since Tuesday, the U.S. Supreme Court has been reviewing two cases related to the issue of marriage for same-sex couples. The nine justices must decide by June on the constitutionality of a 1996 law stating that marriage is the union of "a man and a woman." If it is repealed, gay marriage could be recognized at the federal level.

The Californian Case

For two days, the Supreme Court has been considering the issue of gay marriage and must rule on the two appeals. The first was carried to the highest court in the country by two gay couples in California. The "wise nine" must consider the ban on marriage for same-sex couples in the most populous state in the U.S. This is stipulated in the California Constitution by an amendment, "Proposition 8," which was approved by referendum in 2008, even though the state had allowed gay marriage just five months earlier.

According to advocates of gay marriage, the amendment violates the equal protection clause of the 14th amendment of the U.S. Constitution, which states that "no state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States." Proponents of Proposition 8 believe that the repeal should go to Congress rather than the Supreme Court.

An Unconstitutional Federal Law?

The second case which the justices will discuss is the Defense of Marriage Act, which states that marriage is the union between "a man and a woman." This law accords different rights to same-sex couples, while nine of the 50 states and Washington, D.C. have allowed gay marriage, the first being Massachusetts in 2004. This is not currently recognized at the federal level. The Supreme Court could therefore find this law unconstitutional.

Toward Legalization of Gay Marriage?

Does a victory on these two issues for U.S. supporters of "marriage for all" mean that it will be legalized? The probability is very low, say U.S. constitutionalists, who particularly emphasize that the Supreme Court is an institution that advances "in stages." If the Supreme Court simply legalizes gay marriage, it would render the law in 31 other states unconstitutional. These states, like the federal Constitution, define marriage as the union between a man and a woman.

In their decision, expected by June, the justices may simply repeal DOMA. In this case, married same-sex couples could receive additional rights at the federal level, particularly in relation to tax or estate. The situation looks very indecisive in California: If Proposition 8 is repealed, the state could become the 10th to legalize gay marriage. Or the Supreme Court could not decide or reassure the proponents of the amendment. In this case, homosexuals retain the right to civil unions, which guarantee the same rights as heterosexuals, like in eight other states. Voting conservative Justice Anthony Kennedy already claims to be decisive.

The Clintons Support the Obama Administration

The U.S. president officially supports gay marriage before the Supreme Court. The Obama administration argues for both the repeal of DOMA and the amendment in California, although it is not involved in this second case. "Every American should be able to marry the person they love," the Democratic leader tweeted on Monday night. A year ago, before his re-election to the White House, he announced for the first time that he personally supports gay marriage.

His predecessor, Bill Clinton, also caused a sensation at the beginning of March by asking the Supreme Court to repeal the law he had validated. The former president also feels that DOMA is now "discriminatory" in states where gay marriage is authorized. His wife, Hillary Clinton, has announced her support of the legalization of marriage for same-sex couples. "My personal views have been shaped over time,” assured the ex-secretary of state, while others analysts see in this position the beginnings of a candidature for the 2016 elections. "You can't be a Democratic candidate in 2016 and oppose same-sex marriage,” explained Ben La Bolt, spokesman for Barack Obama’s last campaign last week.

A Democrat-Republican Divide?

While a majority of U.S. citizens support gay marriage — 52 to 58 percent, according to recent surveys, a figure which has grown steadily for more than a decade — public opinion is very divided according to age, religion and political positioning. According to a Pew Research Center poll released in mid-March, 66 percent of Democrats favor legalization, compared to 38 percent of Republicans. At the political level, the two political camps are also experiencing some exceptions. Some Democrats, such as Jon Tester and Joe Donnelly, senators from Montana and Indiana respectively, are against the idea of gay marriage. Among Republicans, several prominent personalities also differ in the other direction. Ohio Senator Rob Portman and former party chairman Ken Mehlman are in favor of legalization. Former Republican primary candidate for the 2012 presidential election Jon Huntsman pleads for civil unions.