What law did they break? Their actions were terrorizing. They were purposely, without provocation, causing the passengers to fear for their own safety...and the so-called "holy" men knew it. The imams sat like the terrorists did on 9/11, they asked for the seat belt extenders, just to name a few actions.
Who knows how the terrorists sat on 9/11? I thought seating assignments were made by the boarding crew, or when booking. Certainly, not sitting together is not a "terrorist" act. Did the imams receive seat belt extenders from the stewardesses? If so, they couldn't have been all that concerned. Should we become afraid of middle-eastern looking men who wear sturdy belts when boarding an airplane?
How do you know that it was their intent to cause fear in the other passengers?