“Was this based on the state or federal constitution?”
In theory this can’t be based on the Federal Constitution since marriage is strictly a state issue. Marriage is not mentioned in the Constitution. On the other hand, far be it from leftwing judges to find rights in the Constitution that don’t exist.
Ironically, the right to license is the right to deny. If a license can be had by anyone who wants it, then there is no purpose to a license. I bet you can’t get a plumbers license in Iowa unless you are a plumber. Isn’t that discrimination against non-plumbers who want to lay pipe?
A number of SCOTUS rulings have recognized marriage as a "fundamental right"
Loving v. Virginia (unanimous)
Zablocki v. Redhail (8-1)
Turner v. Safley (the concur/dissent was split by different sections of the ruling)