25 C.F.R. § 141.31
(a) Except as authorized in this section, no person employed by the U.S. Government in Indian Affairs may have any interest in any trade with an Indian or an Indian organization. Employees of the U.S. Government may trade with an Indian or Indian organization for any purpose other than to engage in a profit-making activity under the following conditions:
(b) Lease or sale of home sites or allotments on trust or restricted Indian land to or from Indian employees of the U.S. Government shall be made on sealed bids, unless the Commissioner waives this requirement on the basis of a report showing:
(3) That the consideration for the proposed transaction is not less than the appraised value of the land or leasehold interest unless the Indian employee qualifies and is intending a transaction in accordance with § 152.5 (b) and (c) of this chapter or § 162.5(b)(1), (2) and (3) of this chapter.
An affidavit, as follows, shall accompany each proposed land transaction:
I,____________________________(Name) ____________________________(Title) swear (or affirm) that I have not exercised any undue influence nor used any special knowledge received by reason of my office in obtaining the (grantor's, purchaser's, vendor's) consent to the instant transaction.
[40 FR 39837, Aug. 29, 1975, as amended at 41 FR 3288, Jan. 22, 1976. Redesignated at 47 FR 13327, Mar. 30, 1982]