1. As soon as KSM and his fellow terrorists set foot on American soil, they have all of the rights of an American citizen.  Even though Guantanamo Bay houses a U.S. military base, it is not considered to be on American soil.  I know that because my sister was born at Gitmo.
2. Once in America, each of these terrorists is considered innocent until proven guilty by a court of law.  They will be only suspects and not convicted criminals.
3. Trying terrorists by military tribunals if they commit their acts outside of America but trying them in American courts if they commit their crimes inside this country sends the wrong message.  It tells the terrorists that they will receive rights normally afforded to only American citizens if they kill innocent people within American borders.
4. KSM was not read his Miranda rights because he was captured on the battlefield in Pakistan.  Since he was not Mirandized, then he will have automatic appeals granted if he is convicted.  Much evidence will likely be inadmissable because his rights were not read, and statements that he made were not made with legal counsel present.
5. Because KSM was waterboarded more than 180 times, any statements that he gave after that point could be excluded from the trial due to being obtained via coercion.
6. The discovery phase of this trial will turn over highly sensitive intelligence information to KSM's lawyers.  If he chooses to represent himself, then American intelligence information will be turned over to Al Qaeda via KSM.  This information may contain not only our intelligence practices but possibly names of agents and also those from other countries who assisted America in the war against terror.
7. There is no guarantee that these men will be convicted.  This will depend upon the judge, the jury, and the evidence that is allowed in court.  KSM's lawyers will certainly insist that at least one Muslim be on the jury.
8. If acquitted, these terrorists will be released in America.
9. The terrorists will be portrayed as the victims in this trial.  They were "tortured" and not Mirandized.
10. This trial will give these terrorists a platform to spew their propaganda and hatred for America.
11. America itself will be put on trial, particularly those who kept us safe.
12. A possible motive for bringing these terrorists to America could be to put the Bush administration and the CIA on trial.  Although they cannot be convicted in this trial, "evidence" discovered in it could be sent to the ICC in the Hague to force the World Court to bring charges against President Bush, Vice President Cheney, and others who protected this nation.
13. People will think very carefully before working for the CIA, and other countries will be less willing to help America after their intelligence secrets are exposed in this trial.
14. Attorney General Holder has a conflict of interest in terrorism cases since he was a senior partner at a law firm that defended terrorists in the past.  He also, as Deputy Attorney General in 2000, was involved in the pardon of the FLN terrorists.
15. President Obama and Attorney General Holder have both already judged KSM as being guilty and that he will receive the death penalty.  This is illegal since KSM has not yet had his day in our courts and therefore must be considered innocent until proven guilty.  For example, after the Manson slayings in the 1960's then President Nixon was rebuffed for indicating that Manson and his gang were guilty of the crime before they had their day in court.
16. The pre-judging of these terrorists as being guilty breaks a guarantee that Americans have always held dear - the right of presumed innocence.  This is bad precedent that could later be done to American citizens since trying these foreign terrorists in American courts will blur the lines between American citizens and foreign enemy combatants.
17. Because these terrorists were not Mirandized, this could set another precedent that could later be applied to American citizens.  Lawyers frequently use prior cases as "case law", applying what decisions were made there to current cases.
18. Military tribunals were already underway in Gitmo where KSM was being tried.  This was halted in January, 2009 after a change in the U.S. Presidency.  KSM pled guilty in the military tribunal and wanted to be put to death.

I see nothing good coming out of this decision by Obama and Holder.