"Actually, it's quite low as they don't actually have to prove it at all. "
Well actually, the govt did not een address the Amendment in their argument which IMO was why they had such a difficult time convincing the court.\
http://www.independent.org/newsroom/article.asp?ID=1247
"Commentary
Jose Padilla: A Constitutional Challenge for Us All
December 18, 2003
Brigid O'Neil
In a landmark victory for constitutional protections and the separation of powers in the post-9/11 era, a panel of the 2nd U.S. Circuit Court of Appeals issued a 2-1 ruling barring the president from declaring a U.S. citizen an "enemy combatant" without congressional authorization. In a decision likely to influence another case on enemy combatants before the Supreme Court case, the federal appeals court ordered the government to release U.S. citizen Jose Padilla from military custody in thirty days, with the option of transferring Padilla to civilian authorities for a criminal trial."