California Code, Penal Code - PEN § 3049

In all other cases not heretofore provided for, no prisoner sentenced prior to July 1, 1977 may be paroled until he has served the minimum term of imprisonment provided by law for the offense of which he was convicted, except that in cases where the prisoner was serving a sentence on December 31, 1947, and in which the minimum term of imprisonment is more than one year, he may be paroled at any time after the expiration of one-half of the minimum term, with benefit of credits, but in no case shall he be paroled until he has served one calendar year;  provided, that any prisoner, received on or after January 1, 1948, at any state prison or institution under the jurisdiction of the Director of Corrections, whose minimum term of imprisonment is more than one year, may be paroled at any time after the expiration of one-third of the minimum term.  In all other cases he may be paroled at any time after he has served the minimum term prescribed by law.