Holder said in a speech in New York on Saturday that same-sex couples will receive many of the same rights as their heterosexual counterparts. Under the guidelines to be released today, federal prosecutors won't object if a same-sex spouse declines to provide testimony that might incriminate his or her partner.

That policy shift is the most recent instance of Holder staking out the administration's views on contentious issues such as drug laws and voting rights. Last month, Holder's deputy James Cole urged defense lawyers to help the government identify imprisoned drug offenders who should win clemency because they were sentenced under stricter laws than exist today.

"The Justice Department's role in confronting discrimination must be as aggressive today as it was in Robert Kennedy's time," Holder said, citing a crusading predecessor in his speech as a model for an activist approach. "As Attorney General, I will never let this department be simply a bystander during this important moment in history. We will act."