Efforts to learn the details of that communication, or even to target Anwar Al-Awlaki militarily, may be hindered by his status as an American citizen. In addition, ABC News reports that a new Senate report raises concerns about dozens of American converts to Islam, including "blond-haired, blue-eyed types," who are believed to be in Yemen undergoing terrorist training. The full Senate Foreign Relations Committee report can be seen here.
Awlaki, a U.S-born cleric, has been in Yemen since 2004. He told Al Jazeerah that he gave Nidal Malik Hasan his blessing to carry out the Fort Hood massacre November 5. Reports say he also had direct contact with Umar Farouk Abdulmutallab, who was burned trying to ignite an explosive smuggled aboard a flight from Amsterdam in his underwear Christmas Day.
It's not clear whether officials have been able to study the content of all the emails. In some cases, it might be innocent communication from relatives or friends, or general religious questions. The greater concern, however, is whether some could be seeking religious justification for an attack, something that would replicate what Awlaki has described about his communication with Hasan.
Hasan's attack was justified, Awlaki said:
"Because Nidal's target was a military target inside America, and there is no question about this. Then, also, those members of the military [i.e. the victims] were not regular soldiers; rather they were prepared and preparing themselves to go to battle and to kill downtrodden Muslims and to commit crimes in Afghanistan."
Sources say law enforcement and intelligence agencies may not have enough information to open preliminary investigations and learn more about the content of communication with Awlaki.
As an American citizen, Awlaki still enjoys the same civil rights as anyone in the United States. Similarly, U.S. intelligence officials believe they could have used a Predator drone strike to try to kill Awlaki, but held back because he's an American, the IPT has learned.
That needs to change, said a senior US lawmaker who spoke to IPT News.
"Where you have people like Awlaki – who is clearly inspirational and operational in Al Qaeda in the Arabian Peninsula – we need to be able to put them in position where the U.S. military and U.S. intelligence can go after them for the people they are," the same lawmaker said in an interview. "We need to be able to find, capture and if necessary kill these individuals before they do any more harm to the United States."
That could mean the U.S. is gearing up to name Awlaki a Specially Designated Global Terrorist. That status could make him vulnerable to military action and allow law enforcement to learn more about those in communication with him.
According to Politico's Josh Gerstein, Secretary of State Hillary Clinton quietly designated Al Qaeda in the Arabian Peninsula as a terrorist group December 14.
IPT News has learned that intelligence officials were trying to learn more about Awlaki's communications. He exchanged at least 18 emails with Hasan in the year leading up to the Fort Hood shooting. "He was asking about killing American soldiers and officers. [He asked] whether this is a religiously legitimate act or not," Awlaki told Al Jazeerah.
Declaring Awlaki to be a Specially Designated Global Terrorist would help because this status would prohibit sending money or other forms of material support to him, said Barry Sabin, a former prosecutor in the Department of Justice's Counterterrorism section.
"He becomes radioactive" with a designation, Sabin said.
Robert Blitzer, the FBI's domestic terrorism chief in the 1990s and now a homeland security consultant with ICFI International, said there are things that law enforcement and intelligence officials likely are doing to build a case to monitor those communicating with Awlaki.
"You're going to try your darndest to get enough information to open a preliminary inquiry," he said.
Once someone is identified, you "would immediately check every record you might possibly have" on them and conduct link analysis to see if there are any other connections, Blitzer said. That includes other activities such as seeking weapons permits, which, alone, wouldn't be illegal but could mean more in connection with the communication.
"You're looking at that spider web of contacts."
It's reasonable to assume Awlaki's reach extends far beyond those already publicly identified. His sermons, including "Constants on the Path of Jihad," are considered to have been influential in terrorist plots in Fort Dix, Ontario, New Jersey and England.
Other reports indicate there are tens of thousands of Americans and other westerners in Yemen being radicalized. At some point, they will return, like Abdulhakim Mujahid Muhammad, who killed an Army recruiter in Little Rock June 1.
ABC News reported Tuesday that a new Senate Foreign Relations Committee report finds as many as three dozen Americans, most of whom converted to Islam while serving in New York prisons, have been training in Yemen and could pose a "significant threat" for attacks on America.
In addition, ABC reports that the Senate committee found numerous examples of "blond-haired, blue-eyed types" also in Yemen who have converted to Islam and are feared to be undergoing training for their own possible attacks.
"When are they going to go off? That's the issue," Blitzer said. In the cases of Muhammad, Hasan and Abdulmutallab, the terrorists were well educated and came from relatively comfortable backgrounds. That increases the challenge for law enforcement and intelligence.
"These are well educated folks who embraced religion to the degree that they're willing to sacrifice themselves."