The way the terrorist is trained to operate, especially the suicide terrorists, makes punishment and the threat of punishment far less valuable to those who would prevent the crime.
The new rule says that the FBI has the right to go to public places on the same terms and conditions as other members of the public for counter-terrorism purposes.
The FBI. is a massive culture. It's been a culture that served America well, and it's been focused on prosecution. But what we need in terms of terrorism is prevention.
It doesn't help to wait until something happens and then prosecute the offenders, especially if it's the idea of the offender to extinguish himself in the commission of the crime.