In JJH Enterprises Ltd (Trading As ValueLicensing) v Microsoft Corporation & Ors  EWHC 929 (Comm) Picken J makes a debatable point in his discussion of a forum non conveniens application by defendants, Microsoft.
In the proceedings ValueLicensing claim damages arising from alleged breaches of competition law by Microsoft. The claim is a ‘stand alone’ one, not a ‘follow-on’ one. There is no underlying infringement decision of the European Commission (or any domestic competition regulator) on which ValueLicensing can rely to establish that an infringement of competition law has been committed.
Some of the Microsoft entities firstly seek summary dismissal of the case against them, arguing they cannot be held liable for an alleged infringement of either Article 101 or 102 TFEU as a result of an overall Microsoft ‘campaign’ in which they did not demonstrably take part. Here  ff there is interesting discussion ia of Provimi (Roche Products Ltd. & Ors v Provimi Ltd  EWHC 961 (Comm)), which held that an entity that implements an agreement in breach of A101 to which a member of the same undertaking is a party can be held liable for the infringement even though the implementer itself does not know of the infringement. Specifically, whether Provimi was wrongly decided following from Cooper Tire Europe Ltd v Bayer Public Co Ltd  EWCA Civ 864 – this is an issue for which CJEU referral is not possible post Brexit.
The judge however refers to the broader concept of ‘undertaking’ in the A101-102 sense following eg CJEU C-882/19 Sumal SL v Mercedes Benz Trucks Espana SL. Sumal, Picken J holds , is relevant authority both pre and post Brexit.
Quite how parties see a difference in the lex causae for the competition law infringement pre and post Brexit is not clear to me. Pre Brexit it is said to be ‘English law’ (held to include 101-102 TFEU prior to Brexit), full stop, while post Brexit that law is said to be determined by (retained) Article 6 Rome II, which for same of the claim will be English law as being one of the ‘affected markets’ per A6 Rome II.
It is in the forum non application that the judge posits  that an important consideration of England as the more appropriate forum, is
it is clear that Microsoft UK’s position at trial will be that in certain material respects English law has taken a divergent path from EU law. In such circumstances, it would be wholly inappropriate, and certainly undesirable, for a court in Ireland to be determining whether Microsoft UK is right about this. On the other hand, there would be no difficulty with the Court here applying EU competition law, either as part of English law (in respect of the pre-Brexit period and, if that is what the Court determines is the case, also in respect of the post-Brexit period) or as part of the laws of other EU/EEA member states, since the Court here is very experienced in doing just that.
If it is true that under forum non, only English courts can be held properly to determine the direction of English law post Brexit, the hand of many a claimant in forum non applications will surely be strengthened.