Punishment for crime involves both judicial and executive discretion.  The sentence in years (or life) is imposed by the trial court, but where the convict actually is in those years is typically an executive decision.  That may involve which prison he is sent to, whether he is inside or outside prison (i.e., parole), or even which country he is in.

Khalid Al Fawwaz was sentenced today for his part in the 1998 Embassy Bombing plot.  He received three life sentences and a ten-year sentence, concurrent.  And Judge Kaplan added this:

The Court makes the following recommendation to the Department of Justice: The Court is mindful of the fact that defendant may have the ability to apply to the U.S. Department of Justice under the international prisoner transfer program to be allowed to serve some or all of his sentence in another nation. Although a decision on any such application, if one is made, would be up to the Department of Justice, the Court strongly recommends that any such application be denied. The defendant has been convicted of very serious crimes against American citizens. His punishment ought to be served in, and more particularly, always remain under the control of the United States of America.

Now that's refreshing to hear from a federal judge.