Registered domestic partners and married spouses must now be treated the same under the California Insurance Equality Act (AB 22081/2005, Insurance Code §10121.7. (a) & §381.5)

Some Insurance Companies  allow Heterosexuals, to be covered, if the Employer wants to provide for that option.  See question 7 g on the sample Employer Group Health Insurance Application - it may also be a law... Here's a sample  certification form for domestic partnership arrangements.

Consumer Links

Blue Shield FAQ's

Q & A Equality CA Website,

Summary - PJ Hoskins, Esq.

Nolo Press A Legal Guide for Lesbian & Gay Couples

737 Publication2010 Tax Information for Registered Domestic Partners

776 Publication2010 Tax Information for Same-Sex Married Couples

Law Excerpts

Insurance Code §381.5. (a) Every policy ...shall provide coverage for the  Domestic Partner Registry of an insured or policyholder that is equal to, and subject to the same terms and conditions as, the coverage provided to a spouse of an insured or policyholder. ...This subdivision applies to all forms of insurance regulated by this code.

Insurance Code §10121.7. (a) A policy of group health insurance that provides hospital, medical, or surgical expense benefits shall provide equal coverage to employers or guaranteed associations, as defined in Section10700, (f) or the  domestic partner Registry

Family Law Code §297-297.5(5) Either of the following:
   (A) Both persons are members of the same sex.
   (B) ... persons of opposite sexes may not constitute a domestic partnership unless one or both of the persons are over the age of 62.
 

Family Law Code- DOMESTIC PARTNER REGISTRATION:

DEFINITIONS §297-297.5
REGISTRATION §298-298.5
TERMINATION  §299-299.3
LEGAL EFFECT PREEMPTION  §299.6