Here are the differences:
First, the new version requires proof of “substantial” support of Taliban or Al-Qaeda forces, while the former version required proof of “direct” support of such forces.
Second, the new version requires proof of “substantial” support of forces (other than Taliban or Al-Qaeda) engaged in hostilities against the U.S. and its coalition partners, while the former version only required “support.”
And, third, the new version applies to a person who “directly” supported hostilities to aid enemy armed forces, while the former version only required “support” of such hostilities, and did not include the word “armed” as to enemy forces who had been supported.
The practical effect of this position is to strengthen the case, legally and politically, of the more marginally culpable individuals detained at Guantanamo Bay, Cuba by U.S. forces as enemy combatants, in part in the hope that admitted terorrists and more culpable individuals who remain there can still be detained indefinitely, probably in some U.S. prison or military brig.
The Obama administration is also relying strictly upon the Authorization for Use of Military Force declaration from Congress, rather than the inherent powers of the President as Commander-in-Chief. This is notable because the 2001 AUMF applies only to people appropriately connected to "the terrorist attacks that occurred on September 11, 2001, and persons who harbored those responsible for those attacks," and to "persons who were part of, or substantially supported, Taliban or al-Qaida forces or associated forces that are engaged in hostilities against the United States or its coalition partners."
Outside the arena of the war in Afghanistan (and neighboring areas like Northern Pakistan), this is quite a small subset of all people who are terrorists or allies of potential military adversaries. It would exclude, for example, individuals affiliated with the "Real IRA" of Ireland, the Tamil Tigers of Sri Lanka, or, in all likelihood, perpetrators of the Mumbai terrorist attacks of Thanksgiving 2008.
Then again, the Obama administration has simply argued that the President's power to conduct foreign affairs and act as commander-in-chief, is inapplicable to the very specific situation of Guantanamo Bay, Cuba, not that the President is entirely without authority to act outside the criminal justice system against foreign terrorists in general. But, the existence, scope and source of James Bond-like license to kill authority for U.S. government agents acting at the direction of the President against people believed by the President to be national security threats is not entirely clear. Such cases have largely escaped the courts, in part due to legal doctrines like the "state secret doctrine" (which the Obama administration has defended), the requirement of legal standing to bring suit, absolute and qualified governmental immunities to civil rights liability, the War Powers Act that abdicates Congressional war making authority for small, short conflicts, and the statutory limitations to the causes of action that do exist, such as the Alien Tort Claims Act.
The Congressional authorization for the war in Iraq, unlike the 2001 AUMF, was less amorphously directed at a non-geographical, non-state actor like al-Qaida, and that Congressional authorization has decreasing relevance as U.S. forces withdraw from Iraq and are government by the additional restrictions of status of forces agreements with the Iraqi civilian government.
The Obama administration has also moved away from the Bush Administration "enemy combatant" to describe the detainees at Guantanamo Bay whose habeas corpus petitions are now being viewed by multiple judges in the U.S. District Court for the District of Columbia.
Then there is the issue of geography. Some judges, particularly in the U.S. Court of Appeals for the D.C. Circuit have placed great importance on the legal status of the place of the detention. But, the U.S. Supreme Court's recent rulings on the issue have been more equivocal and focused on particular facts and circumstances.
[T]he [Obama administration] memorandum asserted that the detention power “is not limited to persons captured on the battlefields of Afghanistan.” It mentioned those who “provide substantial support” to a terrorist network “in other parts of the world,” but did not say what that reference meant — and, thus, did not exclude applying the detention power inside the U.S., when “substantial support” for terrorism is found inside the country. . . .
The memorandum expressly noted that the new definition would only apply to individuals now held at Guantanamo Bay. That leaves out, among other detention sites, the U.S. military jail operated at Bagram airbase in Afghanistan. Earlier, the Obama Administration told Judge Bates that it was not changing the Bush Administration view that the Bagram detainees have no rights to challenge their captivity there.
The question of the right to detain people in the U.S. for suspected terrorism raises the issue of the continued validity of the post-U.S. Civil War case, Ex Parte Milligan which was believed to place great limitations on Presidential detention powers within the United States in places where the courts are functioning, but has been called into question by the Padilla and Al-Marri cases, and complicated by a case involving U.S. military saboteurs on U.S. soil during World War II, and a U.S. Supreme Court ruling on the detention of those of Japanese descent during World War II (and subsequent legislation in reaction to that case).
On the other hand, at this point in time, there is no one in the United States (apart from Guantanamo Bay, Cuba) whom the United States government or any credible source has claimed is detained as enemy combatant (although some U.S. nationals have been detained in Iraq in connection with the U.S. conduct of military operations and support of the Iraqi civilian government there).
All other persons detained in the U.S. are detained under long established doctrines such as those in connection with the criminal justice process, foreign extradition laws, the juvenile court system, the mental health custody process, immigration detention process, civil contempt power, the material witness laws, or the very short term preventative detention in connection with terrorism cases allowed by the U.S.A. Patriot Act. The only people held prisoner under military authority in the U.S., apart from Guantanamo Bay, Cuba, are U.S. soldiers detained in connection with the U.S. military justice system. Of these, only brief military detentions of U.S. military personnel, and some immigration detentions lack meaningful supervision from either civilian courts or courts-martial. Court intervention in immigration cases by writ of habeas corpus is sometimes possible, but is very attenuated and often the government claims that detainees have waived what rights they may have to court review of their detention. Practically speaking, even a U.S. citizen misidentified as a deportable non-citizen might secure relief more quickly by accepting deportation and then applying for assistance from a foreign U.S. embassy, than by trying to secure relief while detained by immigration officials through the U.S. court system. Of course, for non-U.S. citizens, securing any legal rights at all is often dependent upon remaining within the U.S. until legal rights can be adjudicated.
Outside the U.S., U.S. troops and certain people affiliated with them may be detained at U.S. military facilities and subjected to U.S. military justice, and in exceedingly rare cases, federal criminal cases are conducted through a U.S. embassy, but most detentions under U.S. authority abroad are made by U.S. military forces or their agents in places where U.S. forces are engaged in wartime deployments (primarily Afghanistan and Iraq).
The Bush Administration was also widely reported by major news outlets to have a network of CIA prisons across the world for extra-judicially detained terrorism suspects, possibly numbering in the thousands. It is unclear how much of that network remains, in the face of complaints from allied nations where those prisons are located, or how many people remain in that kind of detention.
And, it is also unclear to what extent that U.S. affiliated operatives continue to engage in "extraordinary rendition" which is the process of delivering terrorism suspects to be detained by cooperating countries known to mistreat detainees for interrogation and/or punishment purposes. People detained by foreign powers whose detention the U.S. government does not actually control are clearly beyond the scope of traditional habeas corpus jurisdiction, but the U.S. could conceivably be found liable for civil rights violations under these circumstances, something that has so far not occurred.
President Obama has also made no indication that he has backed away from the position of prior administrations that have claimed the authority to detain and return to the U.S. criminal suspects outside the extradition process, a power that the U.S. Supreme Court has upheld, at least in one Mexican case.
It does appear, however, that the Obama administration has disavowed torture to a much greater extent than the Bush Administration did.
The Obama Administration has also stated that it is continuing to review its policies over the next six months.