In Ontario, the Rules of Court used to (and perhaps still do) provide a mechanism by which a party can inquire into the authority of counsel representing a corporate party. This rule gave rise a line of cases where costs have been ordered against counsel acting without authority.
In B.C., it seems relatively rare for a party to bring an application to inquire into opposing counsel's authority. However, as the decision of Master Caldwell in Tran v. Ha demonstrates, such an inquiry is clearly possible and the consequences may be unfortunate for counsel. In this case, the court ordered costs payable by a lawyer who commenced an action unaware that the client giving instructions was under a Warrant of Committal.
For more info on the subject of client's capacity to give instructions to counsel see an article in The Advocate co-written by Valerie Dixon and myself.