Estoppel - Issue Estoppel
College of Traditional Chinese Medicine Practitioners and Acupuncturists of Ontario v. Federation of Ontario Traditional Chinese Medicine Association (Committee of Traditional Chinese Medicine Practitioners & Acupuncturists of Ontario) (Ont CA, 2015)
In this case the Court of Appeal briefly set out the elements required for issue estoppel to apply to bar the re-arguing of an issue, and some useful comments of when parties are the 'same parties' for this purpose:
 In our view, the application judge did not err by refusing to entertain the appellants’ constitutional argument on the ground that it had been conclusively and finally determined against them in the prior proceeding. We agree with his conclusion that the required elements of issue estoppel were made out.
 The three preconditions for issue estoppel are:
1) the issue must be the same as the one decided in the prior decision;
2) the prior judicial decision must have been final; and
3) the parties to both proceedings must be the same or their privies.
See Danyluk v. Ainsworth Technologies Inc., 2001 SCC 44 (CanLII),  2 S.C.R. 460, at para. 25.
 .... The applicable principle is that “litigation is conclusive upon issues actually brought before the court and upon any issues which the parties, exercising reasonable diligence, should have brought forward on that occasion”: Las Vegas Strip Ltd. v. Toronto (City) (1996), 1996 CanLII 8037 (ON SC), 30 O.R. (3d) 286 (Gen. Div.), aff’d (1997), 1997 CanLII 3841 (ON CA), 32 O.R. (3d) 651 (C.A.).
(3) Same parties
 The two individual appellants were parties to the Divisional Court proceeding as was the Federation of Ontario Traditional Chinese Medicine Association. All corporate appellants, except Committee of Certified Acupuncturists of Ontario, share the same registered address and they all share many of the same directors and officers, including the two individual appellants. In the context of these proceedings, this constitutes a sufficient degree of identification among the parties “to make it just to hold that the decision to which one was a party should be binding in the proceedings to which the other is a party”: Re EnerNorth Industries Inc., 2009 ONCA 536 (CanLII), 96 O.R. (3d) 1, at para. 62. In any event, even if the same parties requirement for issue estoppel is not strictly met, permitting the appellants to re-litigate the issue that was determined by the Divisional Court would amount to an abuse of process: see Toronto (City) v. C.U.P.E., Local 79, 2003 SCC 63 (CanLII),  3 S.C.R. 77, at para. 37.