((a)) The provisions of this chapter relating to the transfer of offenders shall be applicable only when a treaty providing for such a transfer is in force, and shall only be applicable to transfers of offenders to and from a foreign country pursuant to such a treaty. A sentence imposed by a foreign country upon an offender who is subsequently transferred to the United States pursuant to a treaty shall be subject to being fully executed in the United States even though the treaty under which the offender was transferred is no longer in force.

((b)) An offender may be transferred from the United States pursuant to this chapter only to a country of which the offender is a citizen or national. Only an offender who is a citizen or national of the United States may be transferred to the United States. An offender may be transferred to or from the United States only with the offender’s consent, and only if the offense for which the offender was sentenced satisfies the requirement of double criminality as defined in this chapter. Once an offender’s consent to transfer has been verified by a verifying officer, that consent shall be irrevocable. If at the time of transfer the offender is under eighteen years of age, or is deemed by the verifying officer to be mentally incompetent or otherwise incapable of knowingly and voluntarily consenting to the transfer, the transfer shall not be accomplished unless consent to the transfer be given by a parent or guardian, guardian ad litem, or by an appropriate court of the sentencing country. The appointment of a guardian ad litem shall be independent of the appointment of counsel under .

((c)) An offender shall not be transferred to or from the United States if a proceeding by way of appeal or of collateral attack upon the conviction or sentence be pending.

((d)) The United States upon receiving notice from the country which imposed the sentence that the offender has been granted a pardon, commutation, or amnesty, or that there has been an ameliorating modification or a revocation of the sentence shall give the offender the benefit of the action taken by the sentencing country.