What is the authority of the police to search for weapons under common law?

Ryan J.A. considered the authority to search those detained. She quoted extensively from Terry v. Ohio with approval. She noted at p. 312 that in U.S. law, the power to search as an incident of detention ". . . relates to a search for weapons and emanates from the necessity to ensure the safety of the police and those in the vicinity of the person detained." It is a markedly different situation than an arrest. She stated at p. 314 that in her view, under Canadian common law, in the context of an investigative detention ". . . the police are entitled, if they are justified in believing the person stopped is carrying a weapon, to search for weapons as an incident to detention."