Number One:  The U.S.A. is a nation of a lot of laws and combined they are called the U.S. Code.  The U.S. Code is broken down into 50 Titles (think chapters in a book).  For example, the U.S.A. has Title 10 of the U.S. Code (Armed Forces) but we also have Title 18 of the U.S. Code (Common Crime). 

Number Two:  Much, much wiser minds than the current crop of lawyers, talking TV pundits, and politicians made sure the U.S.A had a Title 10 (Armed Forces).  This is a key point and needs repeating - much smarter people than the current crop of democrat politicians and democrat lawyers and democrat judges decided long ago the U.S.A. must have both a Title 10 and a Title 18.
 
Number Three:  By blurring the lines between -
a) procedures applicable to domestic crimes committed by ordinary criminals (Common Crime - Title 18) and
b) law of war procedures applicable to the detention of enemy combatants (Armed Forces - Title 10);
Democrats purposely confuse the public to win elections.

Number Four:  Because these jihadi loons are not alleged to have robbed some corner liquor store their actions fall under Title 10 of the U.S. Code (Armed Forces).

Bottom-line:  Not everyone's actions fall under Title 18 of the U.S. Code (Common Crime).  During a period of armed conflict (when 3,000 Americans can be slaughtered in 45 minutes) not everyone is "just" a common criminal.  Current Democrats argue the U.S.A. no longer needs Title 10 (Armed Forces).  Democrats have a Utopian vision of the world and Democrats think everyone on the planet deserves full Title 10 (Common Crime) deliberations... with Johnnie L. Cochran, Jr. as their lawyer.  Democrat objections to Guantanamo are that simple.  Ultimately, these Democrats are motivated by politics, not wisdom.

FOOTNOTES -

“Detainees are held at Guantanamo Bay because of their involvement with or support of al Qaeda and its affiliates during a period of armed conflict, not because they are alleged to have robbed the corner liquor store.  Their actions fall under Title 10 of the U.S. Code (Armed Forces), not Title 18 (Crimes and Criminal Procedure).  Prior to the Treaty of Westphalia in 1648, those captured during armed conflicts could generally expect one of two unpleasant fates: death or enslavement.  The treaty expressed a principle that endures to this day, that persons captured during armed conflicts will be detained and then repatriated upon the end of hostilities,” said Morris D. Davis, Yale Law Journal - 08/14/2007

“Millions have been detained during armed conflicts, most notably during World War II and more recently during the war in Vietnam,” said Morris D. Davis

“Detaining captured enemy combatants without charges or trials and placing them in a position where they are incapable of inflicting harm on us or our allies is entirely consistent with internationally accepted principles that have endured for more than four centuries,” said Morris D. Davis

“By blurring the lines between procedures applicable to domestic crimes committed by ordinary criminals and law of war procedures applicable to the detention of enemy combatants, critics mislead the public,” said Morris D. Davis