"The counterpart of a court's power to prevent its processes being abused is its power to protect the integrity of those processes once set in motion. And in some cases, it is that counterpart power of protection that authorises the grant of anti-suit injunctions. Thus, for example, if 'an estate is being administered ... or a petition in bankruptcy has been presented ... or winding up proceedings have been commenced ... an injunction [may be] granted to restrain a person from seeking, by foreign proceedings, to obtain the sole benefit of certain foreign assets'. Similarly, as Gummow J pointed out in National Mutual Holdings Pty Ltd v The Sentry Corporation, a court may grant an injunction to restrain a person from commencing or continuing foreign proceedings if they, the foreign proceedings, interfere with or have a tendency to interfere with proceedings pending in that court.
The inherent power to grant anti-suit injunctions is not confined to the examples just given. As with other aspects of that power, it is not to be restricted to defined and closed categories. Rather, it is to be exercised when the administration of justice so demands or, in the context of anti-suit injunctions, when necessary for the protection of the court's own proceedings or processes.
Quite apart from the inherent power of a court to protect its own processes, a court may, in the exercise of the power deriving from the Chancery Court, make orders in restraint of unconscionable conduct or the unconscientious exercise of legal rights. If the bringing of legal proceedings involves unconscionable conduct or the unconscientious exercise of a legal right, an injunction may be granted by a court in the exercise of its equitable jurisdiction in restraint of those proceedings no matter where they are brought.
In some cases, the equitable jurisdiction to restrain unconscionable conduct may be exercised in aid of legal rights. Thus, as the respondents correctly contend, if there is a contract not to sue, an injunction may be granted to restrain proceedings brought in breach of that contract, whether brought here or abroad. Similarly, an injunction may be granted in aid of a promise not to sue in a foreign jurisdiction constituted, for example, by an agreement to submit to the exclusive jurisdiction of the courts of the forum.
One well established category of case in which an injunction may be granted in the exercise of equitable jurisdiction is that involving proceedings in another court, including in a foreign court, which are, according to the principles of equity, vexatious or oppressive. Thus, it was said in Carron Iron Company v Maclaren that '[w]here [there is] ... pending a litigation here, in which complete relief may be had, [and] a party to the suit institutes proceedings abroad, the Court of Chancery in general considers that act as a vexatious harassing of the opposite party, and restrains the foreign proceedings.'
In Société Aerospatiale, the Privy Council emphasised that the various cases decided in the nineteenth century with respect to vexation and oppression, including Peruvian Guano Company v Bockwoldt, have continuing significance for the grant of anti-suit injunctions. Those cases establish that the mere co-existence of proceedings in different countries does not constitute vexation or oppression. In particular, Peruvian Guano establishes that 'double litigation [which] has no other element of oppression than this, that an action is going on simultaneously abroad, which will give other or additional remedies beyond those attainable in [the domestic forum]' does not amount to vexation or oppression.
More recently, in Bank of Tokyo Ltd v Karoon, Robert Goff LJ pointed out, correctly, in our view, although without specific reference to underlying equitable principle, that foreign proceedings are to be viewed as vexatious or oppressive only if there is nothing which can be gained by them over and above what may be gained in local proceedings. On the other hand, they are vexatious or oppressive if there is a complete correspondence between the proceedings or, in terms used in Carron Iron Company, if 'complete relief' is available in the local proceedings." [Footnotes omitted]