What is the relevant case law on the issue of custody where one parent has changed residence?

Gordon v. Goertz [1996] 2 S.C.R. is the leading case on the issue of custody where one parent has changed residence and both parties agreed that it sets out the applicable law.

Gordon v. Goertz requires that before a court considers the merits of an application, it first be satisfied that there has been a material change in the circumstances of the child since the last custody order has been made. Here there has been no previous custody order and I am considering the case on an initial basis. However, the parties have signed minutes of settlement and there has been a post‑separation status quo with respect to A. that has operated for over five years. I find this to be a situation analogous to one in which a previous order has been made. Thus, I must consider here whether there has been a change in circumstances before I consider the merits. I am satisfied that there has been. Any change alone is not enough. It must be a change that has altered the child's needs or the ability of the parents to meet those needs in a fundamental way which has materially affected the child and was either not foreseen or could not have been contemplated at the time of the initial order.