No, it is not constitutional because the reasons given for restricting marriage to heterosexuals only do not pass the "heightened scrutiny" test appropriate for use when determining if a minority is merely being oppressed or if the law has any real merit. It has no legitimate purpose.
It can be used to demonstrate that civil unions are a form of segregation and that "separate by equal" does not comply with the constitutional requirement of equal protection under the law.
The Equal Protection clause of the 14th Amendment.
The two most pertinent clauses are: (1) The Equal Protection Claus; and, (2) the Full Faith and Credit Clause.
"Equal Protection" under the 14th Amendment.
Some constitutional principles that might be applied to the issue of same-sex marriage are: the equal protection clause, the full-faith-and-credit clause, the separation of church and state and the freedom of religion. It is important to note that marriage is not explicitly mentioned in the US Constitution.
It was the 14th amendment that was violated. The 14th amendment guarantees equal protection of the laws for every US citizen. Since racial minorities were being segregated, it was not an equal protection of the law
None, however, bans on gay marriage violate the equal protection clause of the 14th amendment.
due process or equal protection of the laws
You're referring to the fourteenth amendment, which establishes naturalism and enforces federal regulation on the state governments.
the right to bear arms. gives citizens the right to carry fire arms
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.
Equal Protection and Full Faith and Credit are usually cited.