It is not. The issue is left up to the individual states.
I don't believe there is anything in the US Constitution about marriage.
The US Constitution
It says nothing. The US constitution does not mention any marriage. However it does say that all US citizens have the right to equal protection under the law.
treason
No. Marriage is an "institution" not a "constitution."
The duties and structure of the executive branch of government are found in the US Constitution. More specifically they are defined in Article 2 of the Constitution.
The US Constitution did not just affect the 3 branches. It created the three branches and defined their purpose and limitations.
The executive branch
Courts have jurisdiction over interpretations of the constitution and can suggest amendments. The supreme court was the only one mentioned in the US constitution.
None. The US Constitution is silent on the subject of marriage and partnerships.
This is a list of U.S. states where the recognition and performance of same-sex marriage is explicitly banned either by the constitution or by statute.Alabama (by constitution and statute);Arkansas (by constitution and statute);Florida (by constitution and statute);Georgia (by constitution and statute);Kansas (by constitution and statute); (Legalization of same-sex marriage is imminent.)Louisiana (by constitution and statute);Minnesota (by statute only);Mississippi (by constitution and statue);Missouri (by constitution and statute; recognition is legal);Montana (by constitution and statute); (Legalization of same-sex marriage is imminent.)Nebraska (by constitution and statute);North Dakota (by constitution and statute);Ohio (by constitution and statute);South Carolina (by constitution and statute); (Legalization of same-sex marriage is imminent.)Tennessee (by constitution and statute)
The US Constitution does not explicitly speak of the requirements for obtaining a marriage license, nor of the legal recognition of marriages. This aspect of family law has historically been left up to the individual states.