Acting Against Former Clients

The Code of Conduct defines conflict of interest as follows:
the existence of a substantial risk that the lawyer’s loyalty to or representation of a client would be materially and adversely affected by the lawyer’s own interest or the lawyer's duties to another client, a former client, or a third person”. 
As a general rule, you should not represent a client for the purpose of acting against the interests of a former client in the same matter; in any related matter; or in any other matter if you have relevant confidential information arising from the representation of the former client that may prejudice that client.  See rule 3.4-10 of the Code of Conduct, and the commentary under the rule.
You may, however, act against a former client if;
  • you inform the former client you propose to act in such circumstances and the former client consents to the new representation; or
  • the new representation is substantially unrelated to your representation of the former client and you do not possess confidential information from the prior representation that might prejudice the new representation.
A lawyer in your firm may be able to act against your former client in certain circumstances and if the law firm has taken certain precautions. (See rules 3.4-10 and 3.4-11 of the Code of Conduct.)
Exercise caution when you propose to act against a former client, and read the provisions of section 3.4 of the Code of Conduct in its entirety.