Across Europe and the United States, law enforcement officials are struggling to reckon with attackers like Mr. Abballa and Omar Mateen, whose shooting rampage this month at a gay nightclub in Orlando, Fla., left 49 dead. They are men who clearly seemed to be building toward violent acts, and whose names had surfaced in terrorism investigations, but who avoided crossing legal lines that could tip off the authorities until it was too late…
A man is in a shop and thinks about stealing an object, said Georges Sauveur, a Paris lawyer who has defended several terrorism suspects…What do you do? You put him in jail?
Mr. Sauveur added, You cant put him in jail unless he takes the next step and attempts to steal something.