treason is the crime of disloyalty to one's nation. A person who betrays the nation of their citizenship and/or reneges on an oath of loyalty and in some way willfully cooperates with an enemy.

One could view the actions taken by Phelps in regards to Saddam Hussein as treasonous in nature (depending on your view I suppose),

"In 2003, before the fall of Saddam Hussein during the Iraq War, Phelps wrote Hussein a letter praising his regime for being, in his opinion, "the only Muslim state that allows the Gospel of our Lord Jesus Christ to be freely and openly preached on the streets." Furthermore, he stated that he would like to send a delegation to Baghdad to "preach the Gospel" for one week. Hussein granted permission, and a group of WBC congregants traveled to Iraq to protest against the U.S. The WBC members stood on the streets of Baghdad holding signs condemning Bill and Hillary Clinton and anal sex.[44] After Saddam was hanged, Phelps released a video commentary that stated that both Saddam Hussein and Gerald Ford (who had died the same week) were now in Hell.

Link citing the letter written to Saddam:
http://www.adl.org/special_reports/w...on_america.asp

Link citing the protest in Iraq:
http://www.frontpagemag.com/Articles/Read.aspx?GUID={91058469-F6DE-4615-8B2A-73CDF3E8FCAC}