Although he calls it "prolonged" detention, that word serves as a euphemism so disgusting that I shudder when I type the words. But others have done a far better job of parsing the President's speech. (See Rachel Maddow's expert deconstruction below).
In addition, Glen Greenwald, a constitutional lawyer and very articulate writer of the blog Unclaimed Territory as usual did a thorough job of examining the implications and the constitutional issues. Speaking of the Constitution, that President Obama chose to deliver that attack on civil liberties and the rule of law at the National Archives in the presence of the original Constitution suggests that he used the Constitution as nothing more than a prop. For Bush it was the "Mission Accomplished" sign.
I appreciate the sort of political bind in which Democrats find themselves. Ever since Willie Horton they have lived in fear that a person released from the custody of some government agency who subsequently commits a crime will give a great campaign issue to the republicans. If someone released from U.S. custody commits or participates in an act of terrorism, then we (and I guess Obama sees this coming) will see the Republicans howling with outrage. "We had him! But then the cowardly democrats let him go!" But recall that Benjamin Franklin once said that those who would trade liberty for safety deserve neither. (And I would add that they will have neither). This from someone who had a price on his head during the Revolutionary War.
We have already seen the U.S. law enforcement mis-use the RICO statue to confiscate property of ordinary people based solely on arrest (without convictions). I wrote about that here. A law promoted as a tool to combat organized crime police subsequently use to confiscate the homes of cancer patients growing their own medicinal marijuana. And have we forgotten about George W. Bush's "free speech zones" or the police round-up of journalists and activists in advance of their doing anything during the Republican Convention last summer in Minneapolis? The notorious "no fly" list which has excluded a baby and a U.S. Senator from flying comes to mind as well. We have seen plenty of examples of laws "intended" for foreigners and/or terrorists used on citizens as well. Speaking of the distinction between "foreigners" and citizens, you may recall the interment of Japanese Americans during WWII.
Rachel Maddow used a reference to the movie Minority Report as a scary example in which police arrest people for "pre-crime" : crimes that they will commit but haven't yet. I find this a good and clever reference to the sort of Orwellian nightmare that lurks behind "prolonged detention." I can think of another movie reference: A World Apart. This film took place in Apartheid South Africa and dramatized an actual, frequent practice of preventative detention. Barbara Hershey's character stays in jail for the legal limited period of detention without charge. Then the police have to release her. She leaves the jail-house then almost makes it to a public telephone before the police arrest her again for another period of detention. Remember this if in response to public outrage President Obama amends his plan to place a time limit on how long the U.S. government entitles itself to detain a person without charge or trial.
Remember back in 2002 when Bush set up his torture regime while his head of the newly created "Homeland Security," Tom Ridge, described civil liberties as "... the most precious gift we offer our citizens." First it starts out as an inalienable right. Then turns into a gift that the government deigns to give to us. How much longer will we keep it?