Article III
Section. 3.

Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort. No Person shall be convicted of Treason unless on the Testimony of two Witnesses to the same overt Act, or on Confession in open Court.

The Congress shall have Power to declare the Punishment of Treason, but no Attainder of Treason shall work Corruption of Blood, or Forfeiture except during the Life of the Person attainted.
We all know that the Syrian rebels contain Al Qaeda forces. By doing things to help them in their effort would appear to fall under the category of giving them aid and comfort. If the U.S. does strike Syria it appears that there would be more than enough witnesses to the act to convict those involved with committing treason. Too bad that no one will hold them accountable.