The Supreme Court of the United Kingdom has just released a policy statement concerning "The Use of Live Text-Based Communications from Court" [PDF]. The nub of the policy is simple and clear:
[A]ny member of a legal team or member of the public is free to use text-based communications from court, providing (i) these are silent; and (ii) there is no disruption to the proceedings in court.
Use of mobile phones from the court is prohibited. And, presumably, no video or still cameras are to be used: the court itself broadcasts proceedings using installed video cameras.
A few exceptions to the broadly permissive policy are set out, having to do with rare occasions when secrecy or privacy is important.
So far as I know, the Supreme Court of Canada does not have a published policy concerning text-based reporting from within the court. Though I was present when, recently, Simon Chester was given permission to use Twitter from within the court.