43 C.F.R. § 3100.31 – Enforceability.

(a) No option to acquire any interest in a lease is enforceable if entered into for a period of more than 3 years (including any renewal period that may be provided for in the option).
(b) No option or renewal thereof is enforceable until a signed copy or notice of the option has been filed in the proper BLM office. Each such signed copy or notice must include:
1. (1) The names and addresses of the parties thereto;
2. (2) The serial number of the lease to which the option is applicable;
3. (3) A statement of the number of acres and the type and percentage of interests to be conveyed and retained by the parties to the option, including the date and expiration date of the option.
(c) The signatures of all parties to the option or their duly authorized agents. The signed copy or notice of the option required by this paragraph must contain or be accompanied by a signed statement by the holder of the option that entity is the sole party in interest in the option; if not, the entity must set forth the names and provide a description of the interest therein of the other interested parties, and provide a description of the agreement between them, if oral, and a copy of such agreement, if written.