The "serious" and "sleazy" leaking over years to the media of documents circulated by the Mahon tribunal in advance of public hearings undermines the work of the tribunal and it has a right to seek an injunction to stop it, Mr Justice Hugh Geoghegan said.
The policy of the tribunal of sending out a "brief" to people who might be affected by material in that brief in later public hearings, and of making the contents of that brief confidential, was reasonable and a permissible restriction on the right to freedom of expression, both under the Constitution and European Convention on Human Rights, he believed.
It would have been possible, the judge also declared, for the court to make an order, of a narrower nature than originally sought by the tribunal, protecting that confidentiality and it was "perhaps unfortunate" that the tribunal had not presented to the High Court a narrower and more precisely worded form of injunction.
However, that should not mean the Supreme Court should take the view that no injunction of any kind should be granted, and he would favour an injunction in terms proposed to the Supreme Court by tribunal counsel.
That order would restrain the media from publishing documents, circulated by the tribunal in advance of public hearings in order to meet fair procedure requirements, before such information has been disclosed at a public hearing of the tribunal or unless the tribunal has given permission for publication.
That proposed order would not apply to documents already in the public domain, but would stipulate that the media could not publish the fact that such documents were part of a tribunal brief.
In a minority judgment allowing the tribunal's appeal against the High Court's refusal to make an order restraining publication of the contents of briefs prior to public hearings, the judge said there did not need to be a special provision in the Tribunals of Inquiries Act or elsewhere before the tribunal could create confidentiality over documents or information. Nor did the judge accept the tribunal does not have inherent powers.
The tribunal's system of delivering advance briefs to persons who might be adversely affected by evidence likely to emerge at later public hearings of the tribunal arose directly from constitutional obligations to observe fair procedures and protect the good names of persons, he said.
If the tribunal did not owe that constitutional obligation, as the courts had found it had, it would be much simpler and more efficient for it to keep everything secret until public hearings.
A constitutional obligation superimposed in this way, and to some extent creating problems for the efficient running of the tribunal, must necessarily embrace any desirable reasonable limitation such as, in this case, the imposition of confidentiality.
Any such limitation could not derogate from the constitutional obligation.
The imposition of a reasonable confidentiality was an element in carrying out the constitutional obligation and there was an implied right, by virtue of the Constitution, to impose it.
The imposition of confidentiality could also be justified under Article 10.2 of the European Convention on Human Rights because the consequential restriction on the right to freedom of expression was necessary for the protection of the reputation or the rights of others.
The fact that the briefs circulated by the tribunal may include documents already in the public domain did not mean confidentiality should not attach to the brief, the judge added.