。
The lawyer decided on a course of action.
Literal
Lawyer [topic-は] action [gen-の] procedure [obj-を] decided.
行動の手順 is 'the procedure/steps of action' = 'course of action.' 手順 ('procedure, sequence of steps') is a workplace/formal word for a defined series of actions. 決定する is the formal 'decide' — 決める is more everyday. The noun-する version gives the sentence a businesslike feel.