Filing Federal income and inheritance tax. They are prohibited from using the joint filing, which eliminates in the case of a partner who is truely dependent, say a blind partner with lots of medical bills and no income, being counted toward the deductions for the one with assets and income.

And if one spouse in a gay marriage dies, the spouse is not allowed to inherit tax deferred as a is true for mixed marriages. The Federal government would not recoginize the community property of California as community property, so if a couple split and the property was divided according to California law, the Federal government would rule that the effective transfer would be a gift, and subject to tax. Alimony would be consider a gift which would not only be subject to income tax but also subject to gift tax.