The California legislature sits in a two-year session known as a biennium.  The current session is the 2015-2016 session.  The first year of the session ended on September 11, 2015.  That was the last day for the legislature to pass bills.  Joint Rule 61(a)(14).

The legislature’s passage of a bill does not necessarily mean that it will become law.  Bills passed by the legislature must be presented to the Governor.  If the Governor signs a bill, it becomes a statute.  If the Governor disagrees with the bill, he or she may return it to the house of origin.  If each house then passes the bill by a 2/3 vote, it becomes a statute over the governor’s veto.  Otherwise it dies.  Cal. Const. Art. 4, § 10(a).

However, the Governor has a limited time to decide whether to sign or veto a bill.  The deadline is October 11 for bills passed on or before September 11 and in his possession after that date.  If Governor Brown fails to return a bill to its house of origin by that date, it will become law.  Cal. Const. Art. 4, § 10(b)(1).  Even though the Governor’s office is in the same building has the Senate and Assembly, the requirement that the bill be physically returned is enforced.  When Pete Wilson was governor, nine bills became law when they were left on a copy machine in the Governor’s office by staff. See Wilson Vetoes Arrive Too Late to Kill Laws.

Assuming a bill has become law, when does it take effect?  You’ll rarely find an effective date in a California bill.  The reason is that the effective date of most bills is prescribed by the California Constitution.  Article 4, Section 8(c)(1) of the Constitution provides

“a statute enacted at a regular session shall go into effect on January 1 next following a 90-day period from the date of enactment of the statute”.  This rule does not apply to statutes calling elections, statutes providing for tax levies or appropriations for the “usual current expenses of the State,” and urgency statutes.  See also Cal. Gov’t Code § 9600.

How do you know whether a statute is an urgency statute?  The Constitution requires that an urgency bill include a statement of facts constituting the necessity.  Urgency statutes must be passed by a 2/3 vote of each house.  An urgency statute may not create or abolish any office or change the salary, term, or duties of any office, or grant any franchise or special privilege, or create any vested right or interest.  Cal. Const. Art. 4, § 8(d).  Because of these requirements, most bills are not enacted as urgency statutes.