Polygamy creates an innumerable host of problems in regards to property rights and inheritance, and is therefore impractical.

Bestiality I personally find kind of gross, but I can't think of a valid reason for legally prohibiting intercourse between a man and an animal (marriage between a man and an animal, however, is a different story).

Marriages become invalidated when one of the partners dies. Therefore, a new marriage cannot be established with a partner who is already dead.

Regarding marriage between earthlings and extra-terrestrials, I will withhold any judgement one way or another until such beings actually appear on our planet (or we on theirs).

You are so wrong. How do you feel about polygamy? Bestiality? Marriage between the living and the dead? Marriage between the living and the alien?

Whether or not marriage SHOULD be a purely religious or contractual issue, with no government involvement whatsoever, is a matter of theoretical debate.

However, the current state of our nation's actual laws has marriage being regulated and controlled by the government. Whether or not that should be the case is beside the point. What matters is that because government is legally involved in the regulation of marriage, government must apply that regulation equally to all people. This is true for all levels of government, federal, state, and local. Marriage is one of the Unenumerated Rights of the 9th Amendment, and therefore government cannot forbid it, as doing so would constitute denying and disparaging the rights of individuals.

9th Amendment: The enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people.
To the contrary, this says that it is absolutely NOT a federal issue. It is at best a state issue, and if not addressed by the state, then it is an individual liberty issue.
Personally, I don't see that marriage is a governmental issue at all, at any level. It is a religious or contractual issue at best.

It's in the 9th Amendment. ;)
http://www.gpo.gov/fdsys/pkg/GPO-CONAN-2...

So show me where marriage is identified as a protected right in the constitution.
Equal protection only says that the law must be applied equally to everyone. It does not mean that everyone is equal in every conceivable social capacity.

Except that the law involves marriage, so it's not logical to say this is about life in general.

Here's the education level of our Federal Judiciary:

From Breitbart: "A federal judge struck down Virginia's ban on same-sex marriage today, an historic ruling with especial resonance on Valentine's Day. Except the history of the historic ruling isn't exactly up to par: Judge Arenda Wright Allen claimed the Constitution declares that "all men a created equal," which is, instead, the first line of the Declaration of Independence."

Read the full article at: http://www.breitbart.com/Big-Government/...

http://www.youtube.com/watch?v=rY0WxgSXd...

I sees your bet, and raises you

http://www.youtube.com/watch?v=04854Xqcf...

Poppycock. That only applies to application of law, not life in general. Totally misconstrued interpretation.

Equal protection clause.