Why Isn't Anwar al-Awlaki in Jail?

According to the Toronto Star, the US citizen and radical imam is pretty clearly giving aid and comfort to the enemy from his new home in Yemen, most recently in this praise of Nidal Malik Hasan's killing spree at Ft. Hood. Why hasn't he been extradited, tried, and jailed or executed for treason?

Given this latest disaster, the FBI, CIA, DIA, and State Department had better have a pretty good explanation...I wonder, will Senator Lieberman have the guts to pursue this matter--or is his announced investigation into the Ft. Hood slaughter mere political grandstanding?

UPDATE: This from Reuters: "YEMEN: Yemen signed an agreement with the United States for cooperation on military intelligence and training , its official news agency reported, as the Arabian peninsula state faces a worsening rebellion in the north. The two countries signed the agreement in Sanaa on Tuesday after two days of talks, the second round of such negotiations, Saba reported."

Why not demand extradition of Anwar al-Awlaki in connection with the Ft. Hood massacre as part of any defense agreement? How could the US act to defend a government which is harboring a terrorist who has just incited and celebrated an attack on a US military base--that's nuts, IMHO...

UPDATE 2: More on al-Awlaki, including a look at his Facebook page, from Pamela Geller.

UPDATE 3: The Weekly Standard's Thomas Joscelyn has more on the FBI's relation to al-Awlaki. IMHO, after reading this article, I would guess that the cleric has been protected for reasons as yet unknown by British (he went to London after 9/11) and US (he has not been extradited from Yemen despite years of openly recruiting online for Al Qaeda) intelligence agencies. I wonder if Senator Lieberman will have the guts to pursue this--and the intestinal fortitude to stand up to charges of "McCarthyism" should he take on the FBI and other intelligence agencies over their manifest failures (or worse)?