For tax and pension benefits, see http://www.losthorizons.com/
Court proceedings - Our courts are a sham. We need to move to common law and abolish our current admiralty based laws. But there are ways around this even in our current system without the need to procure a marriage license.
Inheritance laws - Again, there are ways around this in our current system without obtaining a marriage license. But do read up on ownership in allodial. The government should have no say in what you do with your assets.