The effect of privacy injunctions on third parties
In general, an injunction made against a defendant does not affect a third party.
That proposition is, however, subject to the well-known Spycatcher principle, which is that an interlocutory injunction preventing a person from disclosing private and/or confidential information also prevents third parties from disclosing the information provided they have been given notice of the injunction. The principle is based on the need to 'hold the ring' pending trial: if other people publish the information the claimant is seeking to protect, that will frustrate the purpose of the claimant's proceedings. This is of course the reason why lawyers representing claimants in privacy cases normally circulate to media organisations the details of any injunction they have obtained as soon as possible after it has been made.
Since the Spycatcher principle is based on the imperative of preserving the status quo until the conclusion of the trial, it follows that it no longer applies once the trial is over and judgment has been given: Jockey Club v Buffham  EWHC 1866. This has the odd, but logically sound, consequence that a privacy claimant in possession of an interlocutory injunction is in a sense better off than one with a final order.
Following this week's decision of Eady J in OPQ v BJM and CJM  EWHC 1059, the position may be less straightforward than it seemed. An anonymous claimant had obtained an injunction banning the defendant and her partner from publishing information about his private life. The case was described as "a straightforward and blatant blackmail case" involving the proposed sale of intimate photographs. Copies of the injunction were served on the media; nothing was published; and within a short time the defendants had agreed to provide the claimant with a permanent undertaking not to publish the information in question. As Eady J put it:
In due course, since there was no answer to the claim, agreement was reached between the parties. This included provision for an undertaking to be given to the court not to publish any of the confidential information. Thus the Claimant's legitimate objectives were achieved and there would be no longer any need for the proceedings to be continued against the Defendants or for a trial to take place.
That would generally be an end to the matter, but OPQ was concerned that once a final order was in place, the information might nonetheless be published in the media once it was thought that the Spycatcher restraints had fallen away. He therefore sought a contra mundum injunction, i.e. an injunction binding everyone, not just the parties to the action. The basis for OPQ's concern about future publication is unclear from the judgment: Eady J simply observes at  that there is a "clear risk of publication in the media". But at  he notes that following disclosure by OPQ to various newspaper groups of medical evidence suggesting that disclosure would have serious consequences for his and his family's mental health, the newspaper groups' opposition to OPQ's application fell away. That might be thought to suggest the media were not in fact going to publish the information.
At all events, Eady J decided to grant a contra mundum injunction. His judgment sets out the basis on which he concluded he had jurisdiction to do so despite such injunctions having been granted previously only on very rare occasions. Previous examples are the cases of the child killers Robert Thompson, Jon Venables and Mary Bell, where it was perceived that orders to protect their new identities were required to protect their rights to life and freedom from persecution. Such an order was also made in favour of Maxine Carr, the former girlfriend of the Soham killer Ian Huntley.
Although there was no apparent risk to the lives of OPQ or his family (or if there was, this is not stated in the judgment), Eady J was apparently persuaded that there was a risk of serious adverse consequences, including to their mental health, and on that basis he concluded that there was "unfortunately no other means open to the court of fulfilling its obligation under the Human Rights Act to protect those rights than to grant a contra mundum injunction".
This appears to be a significant extension of the jurisdiction to grant injunctions that bind third parties. In the most recent edition of Tugendhat and Christie's The Law of Privacy and the Media, published just a few weeks ago, the editor’s note:
Contra mundum orders are at the extremity of the court's power, and would not commonly be granted in aid of a private right, except where life or limb was at risk. [13.35]
The passage is an illustration of the pace at which privacy law is evolving. In the meantime, the Court of Appeal, in Ambrosiadou v Coward  EWCA 409, has allowed an appeal against a refusal by Eady J to order an injunction preventing the publication of information about foreign family proceedings. The Court of Appeal's rationale was that an injunction was required to prevent media publication even though it was satisfied that the defendant had no intention of publishing:
In the absence of an injunction, it would seem that there would be nothing to prevent a person, to whom an ineptly redacted copy of the May application notice was sent, actually reading the redacted material, and then publishing any information contained therein. An interlocutory injunction restraining the defendant from publishing such information would prevent such a person from doing so, provided that person had notice of the injunction, pursuant to the so-called Spycatcher principle. 
In Lord Neuberger's view, it was "quite possible that some media organisations have been holding off publishing in the light of the injunction granted ex parte by Maddison J and continued by Eady J pending this appeal". On the face of it, it seems extraordinary that the court should grant an injunction to prevent the publication of private information not because the defendant is otherwise likely to publish it, but because of a "possibility" that the media might do so.
See further sections 3.9 and 10.3 of The Privacy Law Handbook