Plaintiffs Lawrence Moch, Press Robinson, and George Eames appeal the dismissal of their action challenging the apportionment of the East Baton Rouge Parish School Board [hereinafter Board]. After obtaining 1970 federal census figures, on October 14, 1971, the Board voluntarily reapportioned itself in order to comply with “one-man one-vote” requirements articulated in
Reynolds v.
Sims,
Plaintiffs instituted the present action on October 10, 1974. Although plaintiffs did not denominate this claim as a class action, the complaint was otherwise almost identical to that filed in 1972. Again, plaintiffs challenged the constitutionality of the multimember districts in the East Baton Rouge School District. The district court granted the defendants’ motion for dismissal, made pursuant to Fed.R. Civ.P. 12(b)(6), 3 on the ground that the 1972 judgment rendered the present cause of action res judicata. Plaintiffs appealed to this court.
Plaintiffs make only one meritorious argument: 4 that a change in this court’s 5 and the Supreme Court’s 6 opinions regarding the constitutionality of multimember districts has occurred since the 1972 dismissal. Accordingly, plaintiffs argue, had the district court in the 1972 action employed the present constitutional standards of multimember districts, it would not have dismissed the case.
The term “res judicata,” in its broadest sense, covers four distinct types of preclusion: bar, merger, collateral estoppel, and direct estoppel.
See
Restatement of Judgments § 45, Comments (a), (b), (c) and (d) at 175-76 (1942). In the present case, we concern ourselves with the application of bar and collateral estoppel. Under the doctrine of bar, a judgment in a prior suit between the same parties bars a second suit on the same cause of action not only as to all matters offered at the first proceeding, but also as to all issues that could have been presented either for or against recovery.
Baltimore S.S. Co. v. Phillips,
Generally, a postjudgment change of circumstances, either factual or legal, does
*597
not alter that judgment’s effect as a bar to later actions based on the same cause of action. 1B
Moore’s Federal Practice,
¶ 0.415, at p. 2051-52 (2nd ed. 1974).
7
Yet, courts have occasionally rejected strict application of bar and estoppel principles when their use would violate an overriding public policy or result in manifest injustice.
E. g., Dore v. Kleppe,
This panel has discovered three pertinent cases that involve the effect of a change in law on the conclusiveness of a prior judgment in which constitutional claims are involved.
8
In
Whitcomb v. Chavis,
Nor can we accept defendant’s argument that the statutory plan was beyond attack because the District Court had held in 1965 that at that time the plan met the ‘substantial equality’ test of Reynolds. Stout v. Bottorff,249 F.Supp. 488 (SD Ind.1965). . . . Here, the District Court did not order reapportionment as a result of population shifts since the 1965 Stout decision, but only because the disparities among districts which were thought to be permissible at the time of that decision had been shown by intervening decisions of this Court to be excessive.
Id.
at 162-63,
In
Bronson v. Board of Education,
Finally, in
Griffin v. State Board of Education,
[The intervening Supreme Court decisions were] a substantial change in the law and ended further viability of our decision. Now to continue its efficacy would be unjust to those initially and now affected by that order.
Again, when as here private litigation has extensive implications of public import, the rule of res judicata or estoppel is not allowed to stultify reassessment of the prior decision. The public interest supersedes the private interest.
Id. at 1182.
This court is well aware of the value that the bar and estoppel doctrines serve in achieving a finality to litigation and in preventing harassment of a party and a waste of the court’s resources through multiplicitous law suits. We are unwilling to hold, however, that they constitute an absolute from which we must never stray, even when a mechanical application would result in manifest injustice. Rather, we believe that the occasional adoption of an exception to the finality rule when public policy so demands does not undermine its general effectiveness. In the present case, plaintiffs claim that the state has violated certain fundamental rights by maintaining multimember voting districts that unconstitutionally dilute their vote. The court below granted defendants’ motion to dismiss on the basis of the res judicata effect of a 1972 decision. Now plaintiffs aver that through an intervening change in law in both the Supreme Court and this circuit, present law would obtain a different result than that reached in the 1972 judgment of dismissal. We find merit in plaintiff’s contention that the application of traditional finality principles, after a change in the appropriate law, could contravene public policy, especially in light of the importance of their constitutional claim and of the fact that plaintiffs never really had their day in court in 1972 since that complaint was dismissed merely on a 12(b)(6) motion. To apply such doctrines after a significant change in law governing the issue of multimember districts has occurred could mean that the East Baton Rouge Parish School Board would be allowed to continue ad infinitum a constitutionally infirm system outlawed everywhere else. We do not feel compelled to determine in this case whether a supervening change in the case law renders a subsequent claim a different cause of action, thus making collateral estoppel rather than bar applicable, or whether such a change constitutes an “altered circumstance” that renders bar, itself, inapplicable. If public interest in giving effect to changes in this important area of the law outweighs the Board’s interest in finality under one doctrine, one would logically conclude that it would compel the same result under the other rule of preclusion. Therefore, we direct the district court to determine on remand: (1) whether a change in the applicable law clearly has occurred since 1972, thus rendering incorrect the legal principles under which the district court determined the ease in 1972 and (2) assuming such a change has occurred, whether application of traditional res judicata principles would cause manifest injustice. If it answers both questions in the affirmative, *599 neither bar nor collateral estoppel should preclude the present action.
REVERSED and REMANDED.
Notes
. Plaintiffs invoked federal jurisdiction pursuant to 28 U.S.C. §§ 1343(3), 2201, 2202 and 42 U.S.C. § 1983.
. Bryant v. East Baton Rouge Parish School Board, 72-3075 (5th Cir. February 9, 1973).
. Generally, a party cannot base a 12(b)(6) motion on res judicata. That doctrine must be pleaded as an affirmative defense. 5 Wright and Miller, Federal Practice and Procedure: Civil ¶ 1357, at 604-610 (1st ed. 1969). Yet, if the trial court has treated the 12(b)(6) motion as one for summary judgment, its dismissal under 12(b)(6) is not reversible error.
Latter and Sons, Inc. v. Dinkler Hotel Co.,
. Plaintiffs also argue that a change in fact, sufficient to negate the conclusiveness of the prior judgment, has occurred. That is, they contend that two Board elections, in which six blacks have run and lost, have been held since 1972. Prior to the 1972 action no election under the plan had been held; plaintiffs therefore argue that new evidence — the inability of blacks to gain seats on the school board — now exists. This subsequently occurring evidence cannot alter the finality of the 1972 action. 1B Moore’s Federal Practice ¶ 0.415, at p. 2052 (2nd ed. 1974).
Plaintiffs do not argue that the technical requirements of res judicata were not met nor do they contend that the class in the first action was not adequately represented so as to prevent the conclusive effect of the first judgment;
see, Gonzales v. Cassidy,
.
See, e. g., Zimmer v. McKeithen,
.
See, e. g., White v. Regester,
. Moore indicates that while the same rule is applicable generally to estoppel, some jurisdictions have held that collateral estoppel, unlike bar, will not preclude a later suit brought after a change in the relevant law, if injustice would result. 1B Moore’s Federal Practice, § 0.448, at 4731-34 (2nd ed. 1974). We do not decide, here whether such a distinction is generally valid.
. While our research has revealed no case from the circuit directly on point, we have discovered an order by this court, which, on July 29, 1976, directed the United States District Court of the Western District of Louisiana, in an action challenging the election districts of the Rapides Parish Police Jury, to effect a legal election under “present facts and law,” freed from the restraint of this court’s prior view of the law in an earlier challenge to the jury.
Parnell v. Rapides Parish School Board,
