Agents from India's domestic and external intelligence agencies traveled to the US recently to interrogate Headley, who the FBI arrested last month and charged with being part of a Lashkar conspiracy to spread terror in the United States, Denmark and India.
An agent, who was part of the joint IB-R&AW team, told rediff.com that a local court had turned down their plea to meet the Pakistani-American.
"In the United States, it is important to obtain the court's permission before interrogating anyone on its soil," the agent said, requesting that his name not be mentioned in this report.
An application was filed before a local court, but it was rejected, he added. "We were unable to convince the court that we had sufficient grounds to interrogate Headley."
When asked why the team had traveled to the US without completing the groundwork, the agent said IB and R&AW officials had communicated the team's agenda to the FBI who had given them the go-ahead to interrogate Headley.
"But Headley was in judicial custody and we needed the court's permission to question him. We would have had no problems had he been in police custody," the agent added.
A FBI team will visit India next week to investigate Headley's links with the 26/11 terror attacks in Mumbai.
Investigating teams have fanned out to the cities and towns that were on Headley's terror radar as revealed by the FBI probe. These teams have been told to trace Headley's activities diligently and gather information about his plans.