As Dick said, in the US, participation in a civil union (however that might be defined) does not bring with it full Federal government benefits. For example, the spouse (defined for the purpose of this as a member of a marriage, and Federal law defines "marriage" as an exclusively heterosexual relationship) of a Federal employee is covered by his or her health insurance, while a (civil union) partner is not. A spouse is entitled to a share of a living retiree's Social Security benefits, and to a survivor's benefit when the retiree is deceased, while a partner is not. I think (but I'm not certain) that a partner can receive a survivor's annuity under the Federal Civil Service retirement system, but it would be under what is called the "insurable interest" section of the law and would cost significantly more than a spousal annuity.