Section 227.21 - Restrictions on operations(a) All leases issued under the provisions of the regulations in this part shall be subject to imposition by the Secretary of the Interior of such restrictions as to time or times for the drilling of wells and as to the production from any well or wells as in his judgment may be necessary or proper for the protection of the natural resources of the leased land and in the interest of the lessor. In the exercise of his judgment the Secretary of the Interior may take into consideration, among other things, the Federal laws, State laws, regulations by competent Federal or State authorities, lawful agreements among operators regulating either drilling or production, or both, and any regulatory action desired by tribal authorities.(b) All leases issued pursuant to the regulations in this part shall be subject to a co-operative or unit development plan affecting the leased lands if and when required by the Secretary of the Interior, but no lease shall participate in any cooperative or unit plan without prior approval of the Secretary of the Interior.