Nah...
Too broad. Thanks to the Patriot Act, "terrorist" is defined to include 80% of Freepers.
In any case, the EO covers those who were merely "former members" of Al Quaida. Could you imagine the Quirin court allowing FDR to summarily try and execute those who were merely "former members" of the NAZI party?
In any case, over the weekend I had time to read the caselaw on this a bit more closely. Any constitutional challenge will come on a case by case basis as the SC, through writs of habeas corpus, decide whether or not the particular accused is an "unlawful beligerent." However, I doubt that the accuseds will ever be given the chance to file anything; as it is, we have over 1,500 individuals detained incomunicado.