Green v. Green, 2015 ONCA 541:
 An order of costs is discretionary and entitled to deference. The Courts of Justice Act, R.S.O 1990, c. C.43 affords broad discretion to trial judges with respect to costs. This discretion must fit within the framework created by the Family Law Rules, O. Reg. 114/99; M. (C.A.) v. M.(D.) (2003), 67 O.R. (3d) 181 (C.A.).
 An appellate court should set aside a costs award only if the trial judge has made an error in principle or if the costs award is plainly wrong: Hamilton v. Open Window Bakery Ltd., 2004 SCC 9,  1 S.C.R. 303. Thus, the threshold for appellate interference with a trial judge's award of costs is high.