- However, as McHugh JA observed in Cachia v Isaacs (1985) 3 NSWLR 366 at 387 (in relation to an issue which was referred to in Kuligowski at  but not necessary to decide), not all final decisions of ultimate issues by subordinate tribunals are binding as issue estoppels. He continued:
… When a subordinate tribunal is given jurisdiction to decide a particular class of matter, it has jurisdiction to decide not only that matter but all other matters necessary for the exercise of its jurisdiction. But the tribunal has no jurisdiction to determine conclusively, as between the parties, the correctness of the appendant matters. The appendant jurisdiction is collateral or incidental and raises no estoppel.
- That is because, as Jordan CJ explained in Ex parte The Amalgamated Engineering Union (Australian Section); Re Jackson (1937) 38 SR (NSW) 13 at 17, the issue estoppel extends to such matters as are necessarily determined only if the court or tribunal “has jurisdiction to determine these matters for all purposes between the parties, ie, jurisdiction to determine them directly and immediately as well as merely incidentally”. Whereas that will ordinarily be the position in relation to a superior court, it is not necessarily so in relation to inferior courts or tribunals with limited jurisdiction.
- Jordan CJ further explained the position at 19-20:
… But in order that a judicial decision may involve an estoppel as to the matter decided, it is necessary that the tribunal should possess jurisdiction to decide the matter conclusively and for all purposes between the parties, and not merely incidentally and for a limited purpose. In the case of a superior Court, difficulties can seldom arise as to whether estoppel attaches to matters which have been expressly or impliedly decided for the purpose of the direct and immediate decision. This is by reason of the rule that “nothing shall be intended to be out of the jurisdiction of a superior Court, but that which specifically appears to be so”… . But difficulties do occur in the case of subordinate tribunals. Where these have been invested with a general, though limited jurisdiction, matters incidentally decided are res judicatae if they are comprised within the limits of the general jurisdiction of the tribunal: … Where, however, a special jurisdiction is conferred upon a subordinate tribunal to decide some one particular class of matter, the conferring of jurisdiction, although it authorises the tribunal to decide any other matters so far as may be necessary for the exercise of the jurisdiction so conferred, is not regarded as investing it with jurisdiction to decide those matters between the parties conclusively and for all purposes. Such matters are collateral to the matter as to which jurisdiction is conferred. … But unless an intention appears to confer jurisdiction to determine the collateral matters inter partes conclusively and for all purposes … a decision of the tribunal upon a collateral matter lying outside its special jurisdiction creates no estoppel, notwithstanding that the matter was raised and that it was necessary to form an opinion upon it for the purpose of deciding the matter in which the tribunal is invested with special jurisdiction. The reason is that no estoppel can arise from a decision by a tribunal of limited jurisdiction of a matter lying outside its jurisdiction. [Citations omitted]
- The decision of the Privy Council in Attorney General for Trinidad and Tobago v Eriché  AC 518 (which is cited by Jordan CJ and McHugh JA) provides an example. A stipendiary magistrate had jurisdiction to hear and determine a criminal prosecution for digging asphalt on Crown lands without a licence. However no estoppel could arise from the magistrate’s determination that the land was or was not Crown land. Although that question was necessary to decide in order to convict or acquit, the magistrate was not a court having “concurrent or exclusive jurisdiction directly upon the point” (at 523).
- Thus it is necessary to consider the purposes for which any quality of “finality” is ascribed to decisions of a statutory body such as the Commission; as was observed in Maurice Blackburn Cashman v Brown  HCA 22; 242 CLR 647 at , “no greater ambit of finality should be attributed” to the decisions of such a body than the legislation marks out. In that case no issue estoppel arose because the relevant decisions were only final “for the purposes of determining any question or matter arising under or for the purposes” of the Accident Compensation Act 1985 (Vic): at  (emphasis omitted).