This paper argues that the current scope of English anti-suit injunctions risks illegitimate exercise of extraterritorial jurisdiction and should be recalibrated through two underused lenses: (i) lessons from worldwide freezing injunctions and (ii) philosophical accounts of private international law. It distinguishes the anti-suit injunction’s ‘substantive scope’ (whether an equitable ground exists) from its ‘international scope’ (whether England has legitimate regulatory authority in the light of competing foreign interests). Building on the principle of ‘equipage equality’, the paper reframes anti-suit injunctions as procedural devices aimed at maintaining a level playing field in international litigation. It critiques recent English case law for unnecessarily expanding the scope of relief and sidelining the principle of comity. It proposes tighter, theory-grounded ‘checks and balances’: the use of the concept of ‘subject-matter jurisdiction’, insisting on the enforceability of relief as an essential pre-condition, and strengthening protection for respondents through fortified cross-undertakings in damages. The paper calls for an international systemic approach to delimiting the international scope of anti-suit injunctions.