(a) Treaty nation. A country with which the United States has a transfer treaty relationship either through a bilateral treaty or a multilateral transfer convention.

(b) State prisoner. An inmate serving a sentence imposed in a court in one of the states of the United States, or in a territory or commonwealth of the United States.

(c) Departure institution. The Bureau of Prisons institution to which an eligible inmate is finally transferred for return to the country of which the inmate is a citizen or national.

(d) Admission institution. The Bureau of Prisons institution where a United States citizen or national-inmate is first received from a treaty nation.