It's discriminatory and unconstitutional.

For what it's worth, I don't think the government should be involved in marriage in any way, shape, or form. States should issue civil union licenses, IRS 1040 forms should refer to one's civil partner, and medical decisions should be deferred to one's civil partner. In that model, a marriage would be a purely symbolic act between you, your partner, and whatever higher power you believe in. Not the state.

Also, out of curiosity, which of the many biblical models of marriage do you subscribe to?