It appears that if they couldn't make their case, they just lied.

Audit: Anti-terror case data flawed

Only two of 26 sets of department data reported between 2001 and 2005 were accurate, the audit found.

It should not be a default choice. It's like the boy who cried wolf. Just because you can't come up with a case, that doesn't give you the right to charge a person with terrorism related crimes.