What is the effect of Res judicata on an issue that has been decided?

Res judicata and its related doctrines, cause of action estoppel and issue estoppel, prevent the litigation of decided issues or those which could and should have been previously decided. Although their contours vary, their shared goal is to bring finality to litigation. When finality is achieved, the resources of courts and litigants are preserved, inconsistent results are avoided and the integrity of the legal system is protected. For these reasons, when an issue is litigated, the court's judgment, unless appealed, represents its final determination between the parties and their privies. It may not be retried in a later suit between the parties and their privies for a different cause of action: Rivet v. British Columbia, 2007 BCSC 731, paras. 76-88.

Abuse of process is also a related, though distinct, doctrine. It engages the inherent power of the court to prevent the misuse of its procedures such that the administration of justice is brought into disrepute. Accordingly, a litigant may not challenge a court order by means other than an appeal or legal review procedure. This is so regardless of whether the strict requirements for estoppel have been met: Mulligan v. Stephenson, 2013 BCSC 1384, paras. 34-35.