How is a court's determination of reasonable attorney fees reviewed?

A trial court's determination of reasonable attorney fees is reviewed for abuse of discretion. (Laffitte v. Robert Half Internat., Inc. (2016) 1 Cal.5th 480, 488.) '"The scope of discretion always resides in the particular law being applied, i.e., in the "legal principles governing the subject of [the] action . . . ." Action that transgresses the confines of the applicable principles of law is outside the scope of discretion and we call such action an "abuse" of discretion.'" (Lealao, supra, 82 Cal.App.4th at p. 25.)