Leave to appeal
Permission a party must obtain from a court before an appeal can proceed, required for most appeals to the Supreme Court of Canada.
Leave to appeal is the permission a litigant must obtain before bringing certain appeals. Where an appeal lies 'with leave,' the party must first persuade the court to hear the case at all; where an appeal lies 'as of right,' no permission is needed. Most appeals to the Supreme Court of Canada require leave, which the Court grants only where a case raises an issue of public importance.
Leave requirements also apply in many other contexts, such as appeals from interlocutory orders or appeals to provincial appellate courts in certain matters. For researchers, the leave history of a case matters: a notation that leave to appeal to the SCC was refused tells you the lower court's decision stands as the final word in that case, though a refusal of leave is not an endorsement of the reasoning below.