Constructive Res Judicata refers to a legal doctrine where an issue that could have been raised in a previous lawsuit, but was not, is treated as if it was already decided. Essentially, it prevents the re-litigation of matters that were not directly addressed but could have been within the scope of the earlier case. The key difference between Constructive Res Judicata and regular Res Judicata is that the latter applies to issues that have actually been decided in a previous case, while the former extends the rule to issues that were not raised but could have been, thereby barring any future litigation of these unraised issues. Both principles aim to ensure finality in legal disputes, preventing the same issues from being contested repeatedly.