The ruling relies heavily on Romer and Lawrence precedents from the U.S. Supreme Court to find that animus towards gays and lesbians is not a legitimate reason to deviate from equal protection, and that same sex relationships are entitled to constitutional protection. Romer held that a state initiative establishing a state constitutional amendment prohibiting local governments from adopting gay-friendly laws was unconstitutional. Lawrence held that a criminal sodomy law was unconstitutional as applied to consenting same sex adults.
Prior to Prop 8, courts had briefly allowed gay marriages in California. The reasoning is in some ways the converse of a Massachusetts federal district court ruling that held that the federal Defense of Marriage Act was unconstitutional in the context of eligibility for federal benefits based on marital status because the federal government had no authority to define marriage.
Currently, same-sex couples can only legally wed in Massachusetts, Iowa, Connecticut, Vermont, New Hampshire and Washington, D.C.
Many states have enacted same sex couple friendly legislation, like a designated beneficiary law passed in Colorado, and domestic partnership laws, as have many foreign countries. DOMA limits the extent to which marriage in one state applies legally in another, to the extent that it is constitutional.
Meanwhile at couple of key policies at the federal level are changing. The military is in the process of a hotly contested process of "figuring out" how to end the "don't ask, don't tell" policy in favor of a policy that allows openly gay and lesbian service members.
And, the IRS recently held that members of a California domestic partnership which affords full community property rights, are allowed to report half of each partnership member's one-half share of community income and deductions on their individual income tax returns, a treatment that is often more favorable than married filing jointly treatment.
The ruling today on Proposition 8 which passed with 52% of the vote five months after a court ruled that gay marriage must be allowed in the state under the state constitution, and the ruling on DOMA, are both trial court rulings that can be and almost certainly will be appealed. But, they mark a continuing trend of favorable court rulings for same sex couples, and for gay, lesbian and transgender individuals seeking equal treatment under the law.