§1. A diocesan bishop is to admit to a major seminary only those who are judged qualified to dedicate themselves permanently to the sacred ministries; he is to consider their human, moral, spiritual, and intellectual qualities, their physical and psychic health, and their correct intention.
§2. Before they are accepted, they must submit documents of the reception of baptism and confirmation and any other things required by the prescripts of the program of priestly formation.
§3. If it concerns admitting those who were dismissed from another seminary or religious institute, testimony of the respective superior is also required, especially concerning the cause for their dismissal or departure.
Source: Code of Canon Law (Vatican.va)