It is up to the applicant to first show that there has been a change in the "condition, means, needs or other circumstances of the child" under section 17(5) since the last order was made or the court won't change the original order. In the 1996 case of [https://canlii.ca/t/1fr99 Gordon v Goertz], the Supreme Court of Canada talked about the test to vary orders for custody under the old ''Divorce Act'':

<blockquote>[11] The requirement of a material change in the situation of the child means that an application to vary custody cannot serve as an indirect route of appeal from the original custody order. The court cannot retry the case, substituting its discretion for that of the original judge; it must assume the correctness of the decision and consider only the change in circumstances since the order was issued.</blockquote>

<blockquote>[12] What suffices to establish a material change in the circumstances of the child? Change alone is not enough; the change must have altered the child's needs or the ability of the parents to meet those needs in a fundamental way. The question is whether the previous order might have been different had the circumstances now existing prevailed earlier. Moreover, the change should represent a distinct departure from what the court could reasonably have anticipated in making the previous order. "What the court is seeking to isolate are those factors which were not likely to occur at the time the proceedings took place": J.G. McLeod, ''Child Custody Law and Practice'' (1992), at p. 11-5. </blockquote>