California Code, Welfare and Institutions Code - WIC § 216

(a) To any person who violates any law of this state defining a crime, and is at the time of such violation under the age of 18 years, if such person thereafter flees from this state.  Any such person may be proceeded against in the manner otherwise provided by law for proceeding against persons accused of crime.  Upon the return of such person to this state by extradition or otherwise, proceedings shall be commenced in the manner provided for in this chapter.

(b) To any person who violates any law of another state defining a crime, and is at the time of such violation under the age of 18 years, if such person thereafter flees from that state into this state.  Any such person may be proceeded against as an adult in the manner provided in Chapter 4 (commencing with Section 1547) of Title 12 of Part 2 of the Penal Code.  The magistrate shall, for purposes of detention, detain such person in juvenile hall if space is available.  If no space is available in juvenile hall, the magistrate may detain such person in the county jail.