Jeff,
The question currently before us on the issue of marriage is "Should government recognize some marriages, or all marriages?" We might wish there was a law or an initiative representing the alternative "Should government recognize no marriages," but there isn't. There are two public policy choices on the table.
Furthermore, either official recognition of all marriages or official recognition of none could be interpreted as government staying out of
the issue of marriage. If applied automatically to voluntary unions, "recognition of marriage" need entail no more state burden than the type of "recognition" you'd want from government of the change in ownership of a piece of property when a sale takes place. But to recognize some marriages and not others is social engineering, and is undeniably the option that requires the most active role from government. Therefore it is the least libertarian of the three options, and because of the nature of the issue, the least compatible with separation of church and state as well.
Yours in liberty,
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