As used in this subparagraph, the term "reversionary interest" includes a possibility that the policy or its proceeds may return to the decedent or his estate and a possibility that the policy or its proceeds may become subject to a power of disposition by him. In order to determine whether or not the value of a reversionary interest immediately before the death of the decedent exceeded 5 percent of the value of the policy, the principles contained in paragraph (c) (3) and (4) of § 20.2037-1 , insofar as applicable, shall be followed under this subparagraph. In that connection, there must be specifically taken into consideration any incidents of ownership-held by others immediately before the decedent's death which would affect the value of the reversionary interest. For example, the decedent would not be considered to have a reversionary interest in the policy of a value in excess of 5 percent if the power to obtain the cash surrender value existed in some other person immediately before the decedent's death and was exercisable by such other person alone and in all events. The terms "reversionary interest" and "incidents of ownership" do not include the possibility that the decedent might receive a policy or its proceeds by inheritance through the estate of another person, or as a surviving spouse under a statutory right of election or a similar right.
26 C.F.R. §20.2042-1