Cal. Gov. Code § 9109
The determination of the Joint Rules Committee as to the needs of the Legislature shall be subject to change only by action of the committee or by concurrent resolution. If, at any time, the committee determines that there is space in the State Capitol Building Annex in excess of the needs of the legislative branch of the state government, it may release that space for use by the executive branch of the state government until such time as the space is needed by the legislative branch. The release shall be effected by notifying the Director of General Services that certain described space is not necessary for the use by the Legislature for the time being. Thereafter, the Department of General Services, until such time as the Director of General Services is notified that the space has become needed by the legislative branch, shall have the same jurisdiction over the excess space as if this article had not been enacted.
Ca. Gov. Code § 9109