Congratulations to the Republic of South Sudan, the newest state on Earth, for achieving independence last Saturday. And good luck to the new republic; it will need all the luck it can get, notwithstanding its oil and other natural resources. The challenges for it, and for the international community, range from abysmal infrastructure to tribal rivalries to a host of unresolved issues with the country from which it just separated.

The policy challenges for the United States and other foreign powers have to do at least as much with what is left of the Republic of Sudan as with the new state in the south. Sudanese President Omar al-Bashir, who spoke at the independence ceremony, could hardly have sounded nicer. This was especially so given that the occasion, and the negotiations and referendum that led to it, resulted from one of the longest-running secessionist wars in recent decades. Most of that war was fought during the presidency of Bashir, who took power in 1989. And now he has to swallow the fact that it was during his rule that Sudan, which previously had been the largest country in Africa, lost a substantial chunk of its territory and resources. Bashir said he would have preferred the referendum to come out differently but respects the decision of the southern Sudanese people. He also said that he expects the United States to recognize what has happened by lifting its sanctions on Sudan.

And that presents a policy dilemma for Washington. No doubt about it—independence for the south, and Bashir's eventual acquiescence in it, is a big deal. Modern African history is filled with bloody secessionist failures, with Eritrea's separation from Ethiopia two decades ago being the only other success. Elsewhere, the second-youngest state in the world formed through secession—Kosovo—still is not formally recognized as independent by the country from which it split, Serbia (although the two governments have reached some practical agreements on how to conduct unavoidable shared business). Among possible actions that warrant a reward from other governments, the Bashir regime's acceptance of the south's secession has to rank fairly high.

Considering the original impetus for the sanctions, there are additional grounds for acceding to Bashir's wishes. The chief reasons for imposing the sanctions in the 1990s had to do with terrorism. Sudan played host to a long and assorted roster of international terrorists. Osama bin Laden, who lived there from 1991 to 1996, was the best known guest but only one of many. Since then Bashir has gone a long way in cleaning up this part of Sudan's act. His changes in policy have earned favorable comments in successive editions of the State Department's annual country reports on terrorism. But other issues—including the plight of the south—kept intervening, and the sanctions were never removed.

Helping South Sudan get on its feet is another reason for lifting the sanctions. Leaders of the new state have appealed to the United States to do so, in order to avoid impeding South Sudan's export of oil (which will have to be transported through the north).

But—and this is the other half of the dilemma—there is all that other nastiness involving Bashir and his regime, which most recently has included bloody clashes in Kordofan province. The worst of the nastiness has been in the western province of Darfur—bad enough for Bashir to have been indicted by the International Criminal Court on charges of genocide. How can one make any favorable gestures toward such a man, regardless of the nice things he said at the ceremony in Juba? That is the trap of sanctions. Regardless of the reasons for imposing them, they cannot be lifted without being seen more broadly as a reward for the regime that had been subject to them. And whether such a reward seems appropriate, in the eyes of the public of the country that is bestowing it or in the eyes of the international community, is based on opinions about the target regime's overall behavior, not just what it may have done regarding the reasons the sanctions were originally imposed.

I don't have a recommendation for getting out of this particular dilemma, just a reminder that this is the sort of situation one should anticipate when implementing sanctions in the first place.