According to TMZ, Kourtney Kardashian is not allowing the father of her children, Scott Disick, to see their kids until he cleans up his act. Apparently, Scott is abusing alcohol and other substances, which makes Kourtney worried about the dangers his behavior may pose when he's alone with the kids.
In Ontario, if one parent is awarded sole custody of a child, the non-custodial parent will usually be awarded visitation (access) rights. Courts tend to feel that it is in the best interest of a child to maintain a relationship with both parents. As such, child visitation and access rights are rarely denied.
However, access may be denied when there is a history of abuse, neglect, abduction or not returning the child to the custodial parent, or if the child does not wish to see the non-custodial parent. However, even in these circumstances, the court will usually grant supervised or restricted access. For example, a term of an arrangement may require that the parent not be under the influence of alcohol or drugs prior to, or during visitation.
Generally speaking, the custodial parent cannot deny access without a court order. However, access may be denied if visitation is not appropriate, even with restrictions or supervision. This is the case if there are concerns that the child may be harmed if access takes place. Furthermore, Kourtney may be able to refuse access if Scott appears intoxicated when he arrives to pick up the kids. Things aren't looking too good for Scott. He will have to listen to Kourtney and change his ways if he wants to make things work with her and the kids.