Cal. Civ. Proc. Code § 527.3

(a) In order to promote the rights of workers to engage in concerted activities for the purpose of collective bargaining, picketing or other mutual aid or protection, and to prevent the evils which frequently occur when courts interfere with the normal processes of dispute resolution between employers and recognized employee organizations, the equity jurisdiction of the courts in cases involving or growing out of a labor dispute shall be no broader than as set forth in subdivision (b) of this section, and the provisions of subdivision (b) of this section shall be strictly construed in accordance with existing law governing labor disputes with the purpose of avoiding any unnecessary judicial interference in labor disputes.
(b) The acts enumerated in this subdivision, whether performed singly or in concert, shall be legal, and no court nor any judge nor judges thereof, shall have jurisdiction to issue any restraining order or preliminary or permanent injunction which, in specific or general terms, prohibits any person or persons, whether singly or in concert, from doing any of the following:
1. (1) Giving publicity to, and obtaining or communicating information regarding the existence of, or the facts involved in, any labor dispute, whether by advertising, speaking, patrolling any public street or any place where any person or persons may lawfully be, or by any other method not involving fraud, violence or breach of the peace.
2. (2) Peaceful picketing or patrolling involving any labor dispute, whether engaged in singly or in numbers.
3. (3) Assembling peaceably to do any of the acts specified in paragraphs (1) and (2) or to promote lawful interests.
4. (4) Except as provided in subparagraph (iv), for purposes of this section, “labor dispute” is defined as follows:
  1. (i) A case shall be held to involve or to grow out of a labor dispute when the case involves persons who are engaged in the same industry, trade, craft, or occupation; or have direct or indirect interests therein; or who are employees of the same employer; or who are members of the same or an affiliated organization of employers or employees; whether such dispute is (a) between one or more employers or associations of employers and one or more employees or associations of employees; (b) between one or more employers or associations of employers and one or more employers or associations of employers; or (c) between one or more employees or associations of employees and one or more employees or associations of employees; or when the case involves any conflicting or competing interests in a “labor dispute” of “persons participating or interested” therein (as defined in subparagraph (ii)).
  2. (ii) A person or association shall be held to be a person participating or interested in a labor dispute if relief is sought against him or it, and if he or it is engaged in the same industry, trade, craft, or occupation in which such dispute occurs, or has a direct or indirect interest therein, or is a member, officer, or agent of any association composed in whole or in part of employers or employees engaged in such industry, trade, craft, or occupation.
  3. (iii) The term “labor dispute” includes any controversy concerning terms or conditions of employment, or concerning the association or representation of persons in negotiating, fixing, maintaining, changing, or seeking to arrange terms or conditions of employment regardless of whether or not the disputants stand in the proximate relation of employer and employee.
  4. (iv) The term “labor dispute” does not include a jurisdictional strike as defined in Section 1118 of the Labor Code.
(c) Nothing contained in this section shall be construed to alter or supersede the provisions of Chapter 1 of the 1975–76 Third Extraordinary Session, and to the extent of any conflict between the provisions of this act and that chapter, the provisions of the latter shall prevail.
(d) Nothing contained in this section shall be construed to alter the legal rights of public employees or their employers, nor shall this section alter the rights of parties to collective-bargaining agreements under the provisions of Section 1126 of the Labor Code.
(e) It is not the intent of this section to permit conduct that is unlawful including breach of the peace, disorderly conduct, the unlawful blocking of access or egress to premises where a labor dispute exists, or other similar unlawful activity.