Under the laws and regulations of Ontario, Canada, international students under the age of 18 who are enrolled in Ontario school without accompanying of parents, there must be a permanent resident or a Canadian citizen to act as their legal custodian and issue a custodianship letter. Students from China must apply for a study visa if they have the conditions of a guardian and submit a custodianship certificate. At the same time, when underage students renew their study visa, the document must be signed by the custodian.