Ok. Dude. I've seen a whole bunch of people misquoting the constitution and various other important documents that were written by a bunch of dead guys. Here's a little refresher.

"We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness..."

That is a quote from the Declaration of Independence and while this document is a great piece of prose and one hell of a laundry list of complaints against the King, it isn't a part of the constitution and does not endow us with any rights. We do not have a constitutional guarantee to life, liberty and the pursuit of happiness.

The closest we come is in both the fifth and the fourteenth amendments to the constitution which state respectively that:

Amendment V

No person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a grand jury, except in cases arising in the land or naval forces, or in the militia, when in actual service in time of war or public danger; nor shall any person be subject for the same offense to be twice put in jeopardy of life or limb; nor shall be compelled in any criminal case to be a witness against himself, nor be deprived of life, liberty, or property, without due process of law; nor shall private property be taken for public use, without just compensation.

Amendment XIV

Section 1. All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the state wherein they reside. No state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any state deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.

So that's it folks all the magic is in the fourteenth amendment which guarantees us due process in courts and equal protection under the laws.

In regards to the gay marriage issue: the constitution guarantees equal protection under the laws of the nation and states. If a state has a law that says that gay people cannot get married or enter into civil unions, it can (and should) be argued that this is not equal protection for all citizens. However, I think it is important to note that the federal constitution doesn't say anything about marriage one way or the other.

Specifically regarding the California gay marriage debate, this is what the California Statutes Family Code has to say about marriage:

FAMILY CODE SECTION 300:
300. Marriage is a personal relation arising out of a civil contract between a man and a woman, to which the consent of the parties capable of making that contract is necessary. Consent alone does not constitute marriage. Consent must be followed by the issuance of a license and solemnization as authorized by this division, except as provided by Section 425 and Part 4 (commencing with Section 500).

308.5. Only marriage between a man and a woman is valid or recognized in California.

Regardless of your personal feelings on the issue, I think it is important to note that the California Constitution says this about equal protection and the granting of unequal privileges:

Article 1 Declaration of Rights

Section 7
(a) A person may not be deprived of life, liberty, or property without due process of law or denied equal protection of the laws...
(b) A citizen or class of citizens may not be granted privileges or immunities not granted on the same terms to all citizens. Privileges or immunities granted by the Legislature may be altered or revoked.

What does this boil down to? Straight married people are being granted privileges that people in gay or lesbian partnerships are not, and not only is this inherently unfair, clearly it is a violation of California law. So honestly, feel free to argue that Gavin Newsom, and everyone who has been getting married in San Francisco are breaking the law, but the state Constitution is actually on their side.