50 C.F.R. § 37.44
For nonuse, for failure to comply with § 37.14 , or for any action of the permittee not consistent with this part, the Regional Director may revoke or a permittee may relinquish a special use permit to conduct exploratory activities at any time by sending to the other a written notice of revocation or relinquishment. Such notice shall state the reasons for the revocation or relinquishment and shall be sent by registered mail, return receipt requested, at least 30 days in advance of the date that the revocation or relinquishment will be effective. Revocation or relinquishment of a permit to conduct exploratory activities shall not relieve the permittee of the obligation to comply with all other obligations specified in this part and in its special use permit, approved exploration plan and plan of operation. Reconsideration of the Regional Director's actions under this section may be obtained by employing the procedures described in § 37.22(c) . A request for reconsideration shall not operate to stay the Regional Director actions unless such stay is granted in writing by the Director.
50 C.F.R. §37.44