As with most areas of law, the effect of Brexit on English family law is largely unknown. Theresa May has of course promised a 'Great Repeal Bill' enshrining existing EU legislation into UK law, and family lawyers suspect any deviation from the existing rules will be a very low priority for UK negotiators.
In many ways, this will not significantly impact family law. Family law legislation from the EU has largely avoided the question of how family disputes should be decided and focused primarily on where they should be heard. So, for example, all EU countries work to the same list of qualifying criteria for deciding which member states are entitled to hear a divorce application - Brussels IIA not only sets out those criteria but the rule that, if there are two qualifying jurisdictions, the first to be seised will automatically have jurisdiction.
It would be odd, post-Brexit, to find ourselves in a position where the English court is forced to cede jurisdiction to an EU state which was first in time in circumstances where that country would not be obliged to do the same for us. Informal polling of English family lawyers shows strong support for the UK to abandon the first in time approach and revert to the “forum conveniens” approach used for all non-EU jurisdiction disputes. While this will avoid the need for jurisdiction races, it will not necessarily be a good thing as, with huge disparities between different countries’ matrimonial regimes, wealthy parties risk spending huge sums fighting to secure their first choice jurisdiction. This is most recently demonstrated in the case of Peng v Chai (where the husband is thought to be worth over £440m) in which over £5m is said to have been spent arguing about whether the divorce should be heard in England or Malaysia.