Gov. Jerry Brown on Thursday signed AB 517, the bill that ratifies his gambling agreement with the Federated Indians of Graton Rancheria.
The agreement, called a compact, allows the tribe to start work on a 3,000-slot machine casino outside Rohnert Park.
The compact now faces one final governmental hurdle at the federal Department of the Interior, which has 45 days to approve or reject it.
The governor's signature has been expected since the state Assembly passed the bill last week.
The Interior Department is also expected to approve the agreement. If the department does not act, the compact takes effect automatically after 45 days, although it was not clear Thursday when that period begins.
This week, Station Casinos, the Las Vegas company bankrolling the project, said the casino would open to gamblers by the end of 2013.
Before it breaks ground, the tribe must finalize a separate agreement with Sonoma County officials on how it will financially address the casino's impacts.