There’s no specific law that says you have to procreate.
Your celebrant must have authorisation from the state.
Your choice to marry must be made with candid independence.
You can’t marry your siblings, mother, father or descendants.
You can’t marry an animal. You can’t marry a minor.
There must be a grand total of exactly one vagina.
Once married, it’s against the law to marry once again,
Unless you have a proper divorce order, signed in pen.