Marriage is a civil right that everyone has. Gay Amercians are equal to straight americans, therefore since straight americans have the right to marry each other in every state in the U.S.A, gay americans have a constitutuional right to marry their loved ones in every state in the U.S.A.
Constitution Grounds:
Amendment 1 - Freedom of Religion, Press, Expression
Amendment 8 - Protection from Cruel and Unusual Punshiment
Amendment 9 - Construction of the Constitution{The enumeration in the Constitution}
Amendment 10 - Powers of the States and People.
Amendment 13 - Slavery Abolished.
Amendment 14 - Citizenship Rights.
Amendment 26 - Voting age set to 18 years {In some cases}