SAN FRANCISCO—Same-sex marriages resumed in California on Friday afternoon, following a decision by the Ninth U.S. Circuit Court of Appeals to lift the stay on a ruling overturning the state's Proposition 8 gay-marriage ban.

The surprise move sped up the usual timeline for implementing a decision by the Supreme Court, which ruled on Wednesday that a lower-court decision overturning the voter initiative should stand because the original proponents of the law lacked standing to defend it.

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