According to this news report, former President Jimmy Carter thinks that "the detention of terror suspects at the Guantanamo Bay Naval base was an embarrassment and had given extremists an excuse to attack the United States."
One of the problems with discussions about Guantanamo Bay and the war on terrorism is that debates about the legitimacy of detention of enemy combatants gets conflated with debate about the conditions of detention and treatment of detainees (especially with regard to whether detainees are entitled to POW status).
Of course, the latter two matters are significant and important, and to be fair, some of President Carter's complaints pertain to them:
Earlier this month, Carter called for the Guantanamo prison to be shut down, saying reports of abuses there were an embarassment to the United States.
On the other hand, President Carter also gets into the first issue:
He also said that the United States needs to make sure no detainees are held incommunicado and that all are told the charges against them.
But since we are proceeding under the law of armed conflict, there are no "charges" in the sense of violations of criminal law at issue. The detainees are being held as the equivalent of enemy soldiers pursuant to Congressionally authorized use of military force. Specifically:
[T]he President is authorized to use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored such organizations or persons, in order to prevent any future acts of international terrorism against the United States by such nations, organizations or persons.
President Bush has determined that Al Qaeda is the organization that planned and committed the 9/11 attacks, and that the Taliban harbored Al Qaeda. Thus, under the terms of the military force authorization, the President is entitled to use military force against members of Al Qaeda and the Taliban, just as he would be authorized to use military force against the armed forces of an enemy nation against whom Congress has declared war. And in the latter situation (war against another country), there are no "charges" that we need bring against enemy soldiers. There is no access to counsel. They are simply detained until the end of the armed conflict.
Now, it is true that enemy soldiers are typically accorded POW status, which in turn governs the terms of interrogation and so forth. That is why the issues of conditions of detention and treatment of detainees is important; the law of armed conflict permits non-criminal detention of enemy soldiers, but it also requires non-criminal treatment of them.
Thus, I think President Carter is incorrect in arguing that the detainees must be told of the charges against them. (Note: this is obviously different if we seek to punish detainees for violations of the laws of war in a military tribunal.)
Of course, this is not a traditional war between nation-states, where the status of enemy soldiers is readily apparent. Thus, it is not implausible to argue that some process should be available to confirm the enemy status of each individual detainee. Furthermore, there may not be a clear end to the hostilities, as there would be when a peace treaty is signed between countries. Thus, there perhaps should be process available to address whether an individual detainee remains an "enemy." (I offer a proposal to deal with the latter problem in my forthcoming article, Ending the War on Terrorism One Terrorist at a Time: A Non-Criminal Detention Model for Holding and Releasing Guantanamo Bay Detainees, available at SSRN here.)
But even if those additional processes are required, they are a far cry from requiring notice of charges and counsel and so forth. And conflating the alleged abuse at Guantanamo with the legitimacy of detention under the laws of armed conflict further muddles the necessary analysis.