We have seen a number of terrorist activities in Europe where the Police have had the perpetrators on their radar, but due to human rights legislation have not been able to immediately arrest them. The latest incident in Berlin of the lorry driven into a crowd by an IS sympathizer is a clear example, the perpetrator being known to the police, who were unable to detain him due to EU and German legislation.
Whilst this is can be seen as a very slippery slope to a totalitarian regime, we need to understand that we are at war with a bunch of religious maniacs, who have granted themselves the right to slaughter anybody who fails to agree with their distorted mindset.
If we continue on the present path of treating IS with full human right protection, the West will need to come to terms with a massive casualty list and a very protracted war with an adversary who demands total surrender. This is not a war against the Islamic faith as presented in the media, but against a group of religious thugs who have invaded Islam like a fungus and requires all of true Islam, Jews and Christians to fight it.
By taking out anyone who can be identified as potential terrorists by their behavior or by who they mix with immediately, society can buy time to identify the ringleaders and return the remainder after counseling to society.