What is the legal test for authorization of an attorney in a motion for dismissal with prejudice?

An "attorney is authorized by virtue of his employment to bind the client in procedural matters arising during the course of the action but he may not impair the client's substantial rights or the cause of action itself." (Romadka v. Hoge (1991) 232 Cal.App.3d 1231, 1235.) "Clearly a dismissal with prejudice disposes of the client's substantive rights and therefore requires for its validity the authorization of the client." (Id. at p. 1236, italics added.)