Hemain injunctions are temporary injunctions preventing a party from pursuing litigation in a foreign jurisdiction. Its name derives from the Court of Appeal case Hemain v Hemain  2 FLR 388.
When should a Hemain injunction be considered?
Hemain injunctions are useful if the respondent in England is trying to delay the proceedings in England, whilst trying to litigate in a foreign court.
When will they be granted?
The applicant for the injunction must be able to show that the respondent has acted:
vexatiously in obtaining a forensic advantage by delaying proceedings in England while pursuing similar proceedings elsewhere.
This was confirmed by the Court of Appeal in Ahmed v Mustafa  EWCA Civ 277.
Pursuing divorce proceedings overseas by legitimate means, even if motivated by a desire to achieve a more favourable outcome in financial proceedings, is not in itself unconscionable as held in S v S  EWHC 3224 (Fam).
The applicant has no obligation to show that England is the natural forum (R v R  EWHC 2113 (Fam)) and the injunctions are not available where the other jurisdiction is another European Member State (Turner v Grovit (Case C-159/02)  ECR I-3565). It is not yet clear how Brexit will impact this.
Hemain injunctions are an injunction barring the other party. They are not an order against the foreign court. The order may require a party to not take any further steps or issue further proceedings in the foreign court, but there will be no obligation on the foreign court. The foreign court or authority has the discretion to choose whether to continue to deal with the matter. This can mean that the Hemain injunction is ineffective.