What needs to be "re-examined" is our definition of foreign terrorism as a crime. It is not. It is an act of war. It is thus already the responsibility of the military to deal with foreign terrorists. They do not need police powers to do this. The Posse Comitatus Act does not need to be changed.
Civilian law enforcement has no business fighting foreign terrorism. This new "Department of Homeland Security" is unnecessary. The job that they are tasked with is already a DOD function. The idea that we should track down foreign terrorists and put them on trial is ludicrous. They should be attacked and destroyed, just as any other hostile force would be during time of war. Gathering evidence to make a case in court runs counter to that and places the public at risk.
Quite simply, foreigners here suspected of terrorism should be fair game for the military. We need to recognize that these individuals do not have criminal rights under the Constitution as "home-grown" terrorists would. (And it is already the responsibility of domestic law enforcement to catch and try domestic terrorists; another function the "Homeland Security" department is not needed for.) They have no right to a fair trial, nor to freedom from unreasonable search and seizure, nor to due process. Foreign terrorists should be treated as invaders and dealt with in the same manner that regular troops invading our soil would be. Were China to start landing troops on Malibu Beach, would we start swearing out arrest warrants!? Of course not. We'd call in air strikes, not lawyers. Why are terrorists treated differently?
Since foreign terrorism isn't a law enforcement problem, the Posse Comitatus Act is irrelevant to the discussion.