Sole vs joint custody
At law custody refers to decision-making power and not what time children spend with what parent, which is an issue of parenting. There are two types of child custody, sole custody and joint custody.
Sole child custody
Sole child custody occurs where one parent has the right to make major decisions for his/her children without consulting the other parent. Joint child custody exists where parents both have a right to participate in the major decisions of their children. Major decisions relate to matters such as non-emergency medical care, education stream, school and religion.
Joint child custody
There is a strong presumption in favour of joint child custody because the law considers it important for both parents to participate in a discussion about what is in the best interests of their children. As a result, it is difficult for a parent to be awarded sole custody and is most typically reserved for situations where one parent has opted out of their parenting role or is unable to participate in a meaningful discussion about what is in the best interests of children due to mental incapacity or severe addiction.
Occasionally, parents are awarded another type of decision-making regime referred to as parallel parenting. Parallel parenting is when one parent has decision-making authority over one specific set of issues and the other parent has decision-making authority over different issues. For example, one parent is awarded the right to make the decisions relating to the health and recreational activities of the children and the other parent is granted the authority to make education decisions for the children, both religious and scholastic. Parallel parenting is reserved for fairly extreme situations where the parents are both capable of making decisions in the best interests of the children but are completely unable to communicate with each other.
Regardless of the type of custody that is in place if a parent believes that a decision is being made that is contrary to a childs best interest he/she has the ability to make an application and have the court determine what should occur. As such, even parents with sole child custody do not have absolute power and there is a remedy available to a parent that does not have decision-making power.
There is some other useful advice that can be found here.