TMZ has reported that Mike Comrie has responded to Hilary Duff's filing for divorce and has asked for joint custody of their son Luca. As TMZ has reported, the former couple entered into a marriage contract which addresses the legal issues of support and the division of property. However, marriage contracts cannot address the issue of custody. As such, the issue of custody appears as if it will be a contested issue.

In Ontario, "custody" refers to the legal authority to make major decisions regarding a child's health, education and welfare. For married spouses who file an Application or Divorce in Ontario, the legal principles governing custody claims are set out in section 16 of the Divorce Act. In accordance with section 16(8) of the Divorce Act, the court is required to take into "consideration only the best interests of the child of the marriage as determined by reference to the conditions, means, needs and other circumstances of the child". When rendering its decision with respect to custody, a court must be mindful of the maximum contact principle, which refers to the notion that "a child of the marriage should have as much contact with each spouse as is consistent with the best interests of the child".

It is important to note that the day-to-day decisions regarding the child are made by the parent who is caring for the child at that time. Thus, either the "access" parent or "custodial" parent may be responsible for making the day-to-day decisions for the child on any given day. However, the legal implications of where Luca will primarily reside are significant with respect to the issue of child support if the parties resided within Ontario. This is because child support, in Ontario, is determined on the basis of three factors: (1) the income of the payor; (2) the number of children; and (3) the residency arrangements for the children.

If Hilary were to succeed in her claim for sole custody of Luca, it may be presumed that Luca would primarily reside with her. As such, Mike Comrie would have to pay child support to Hilary in accordance with the Child Support Guidelines and his annual income. This conclusion, however, would be dependent on Hilary being able to demonstrate that it is in the best interests of Luca that he primarily resides with her. Furthermore, with respect to the issue of custody, if the parties are able to cooperate with one another in relation to the child, a joint custody arrangement is the more likely result.