Harmonised Union rules on the documents to be issued to applicants should contribute to making it more difficult for applicants to move in an unauthorised manner within the Union. Member States should be able to provide applicants with a travel document only where duly justified serious humanitarian reasons or other imperative reasons arise. The validity of travel documents should be limited to the purpose and duration necessary for the reason for which they are issued. Serious humanitarian reasons could be considered to arise where, for example, an applicant needs to travel to another State for necessary medical treatment which is not available within the Member State in which the applicant is required to be present, to visit relatives in particular cases such as where close relatives are seriously ill or to attend funerals of close relatives. Other imperative reasons could include situations such as attending marriages of close relatives, or travelling as part of a study curriculum or with foster families. The issuance and use of such a travel document does not affect the Member States’ responsibilities under . Member States retain the right to assess applicants’ rights to stay on their territory.