What authority does a trial court have to disqualify an attorney?

"A trial court's authority to disqualify an attorney derives from the power inherent in every court '[t]o control in furtherance of justice, the conduct of its ministerial officers, and of all other persons in any manner connected with a judicial proceeding before it, in every matter pertaining thereto.' [Citations.] Ultimately, disqualification motions involve a conflict between the clients' right to counsel of their choice and the need to maintain ethical standards of professional responsibility. [Citation.] The paramount concern must be to preserve public trust in the scrupulous administration of justice and the integrity of the bar. The important right to counsel of one's choice must yield to ethical considerations that affect the fundamental principles of our judicial process." (People Ex Rel. Dept. of Corporations v. SpeeDee Oil Change Systems, Inc. (1999) 20 Cal.4th 1135, 1145 (SpeeDee Oil).)