Second, in criminal proceedings, jurisdictional errors occur
where a provincial court judge
( i) fails to observe a mandatory provision of a statute; or
( ii) acts in breach of the principles of natural justice.
See Awashish, at para. 23.
 Third, these strict limitations on the availability of certiorari
for parties are to prevent the use of extraordinary remedies as an
end-run to circumvent the rule against interlocutory appeals:
Awashish, at paras. 10-11.
 Fourth, certiorari is not available to parties to review the
conduct of criminal proceedings on the basis of an alleged error of
law on the face of the record: Awashish, at paras. 16-17.
 Fifth, the scope of review available on certiorari for third
parties is somewhat more expansive. After all, third parties do
not have rights of appeal, at least in most cases. Thus, in addition
to review of jurisdictional errors, a third party may invoke
certiorari to challenge an error of law on the face of the record,
provided the order has a final and conclusive effect in relation to
that third party: Awashish, at para. 12.
 It is uncontroversial that a trial judge has jurisdiction or
authority to determine disputes about disclosure. The jurisdiction
is engaged upon request of a party, usually the person charged. It
necessarily follows from this adjudicative authority that the
decision of the trial judge may require a determination about
which disclosure regime — first party or third party — controls
the decision: Gubbins, at para. 29.
 A logical consequence of the authority to determine disclosure issues, more particularly to decide which disclosure regime
governs what is sought, is that any alleged error, at least as
a general rule, would not amount to a jurisdictional error, but
only an error of law in the exercise of jurisdiction. And as we have
already seen, unless the error were to amount to a failure to
observe a mandatory statutory provision or a breach of the principles of natural justice, the error would fall beyond the reach of
certiorari at the instance of any party to the proceedings, but not
a third party.
The principles applied
 As I will explain, I am satisfied that the decision in
Awashish does not foreclose the appellants’ recourse to certiorari
to challenge the disclosure order made by the trial judge in this