Urgency statutes are found in Article IV, Section 8 of the California Constitution. Bills signed into law by the Governor that contain an urgency clause become urgency statutes.
Article IV, Section 8(c)(3) of the Constitution lays out the major difference between a regular bill and an urgency bill. A regular statute goes into effect on January 1 of the year following its passage and signature, or later. Urgency statutes take effect immediately upon being chaptered by the Secretary of State. Of course, a provision in the bill could move back its operative date.
So what makes a statute an urgency statute? Section 8(d) of Article IV specifies that urgency statutes are those that are necessary for immediate preservation of the public peace, health, or safety. Because of this definition, an urgency measure must contain an urgency clause, which specifies why the bill qualifies for the special status based upon this particular constitutional definition. In this regard, Section 8(d) requires a statement of facts constituting the necessity shall be set forth in one section of the bill.
That leads to the second difference between urgency statutes and regular statutes. While most regular statutes only require a simple majority vote to pass. With urgency statutes, there is a floor requirement that there be two votes by legislators on the bill – one on the urgency clause itself, and another on the bill in chief. To pass, both of those votes need to clear a two-thirds supermajority threshold.