Keeva Terry (Roger Williams) has posted Separate and Still Unequal? Taxing California Registered Domestic Partners, 39 U. Tol. L. Rev. 633 (2008), on SSRN.  Here is the abstract:

This article analyzes whether the IRS has a cogent legal basis to discriminate and deny equal treatment to domestic partners. A clear logical framework is outlined, establishing that (i) for federal income tax purposes, the test of taxability is ownership, (ii) ownership is determined by state law, and (iii) according to California state law, domestic partners own community property equally and the earned income of a domestic partner is community property. As an extension of this framework, this article argues that each domestic partner should be required to report one-half of the community income, including any combined earned income such as salaries or wages, as his or her respective income for federal income tax purposes.