The U.S. Senate is preparing to vote on a constitutional amendment to ban gay marriage across the United States. The reasons to support gay marriage are equality under the law, recognition of the equal treatment and dignity of gay people, as well as the social benefits of supporting gay men in stable relationships, such as AIDS prevention.

Even people who oppose gay marriage have reason to support this amendment. However, the United States is a federal republic and marriage law has always been reserved for the state to decide. The Marriage Protection Amendment would nationalize marriage for the first time in the nation’s history.

Congress has already passed a law that no state can be forced to recognize a gay marriage license from another state, so this amendment is not to protect from states like Vermont who have legalized gay marriage; it is more an attempt to create a collective and uniform definition of marriage for all states. This amendment is very unlikely to pass as most Democrats and some Republicans will oppose it, and it requires a two-thirds vote.