Well it's not exactly legal, is it, you prat.
You don't understand what's going on. The things the terrorists hate most are our freedom, democracy, tolerance, pluralism and decency. It's nothing more than provocation on their part. They want you to lower yourself to their level. They're goading you into fighting on their terms. They know that the more we try to tighten our grip, the more radicalised individuals we create. They want you to abandon all the things that make us who we are to fight them. Stop falling for it like an idiot. Stop giving in.
For every person calling for a crackdown, deportations, destruction of mosques, etc, you are the ones attacking the exact same freedoms that the terrorists themselves are attacking. You're giving extremists exactly what they want, namely more extremism and further escalation. You don't defeat terrorists by letting them win.
Try thinking it through to conclusion for a change. There are ways to beat terrorism that don't include debasing your morals to the point that you're no better than they are. Pity you're already there, though. Just don't expect the rest of us to join you.
You will lose if you are not more brutal than they are.
Appeasement does not work. You don't win by letting terrorists operate in your country.
You need to round up Islamists operating your country and expel them.
You need to carpet bomb the ISIS-controlled territory. Wipe them out!!!
You need to ban Islamists from entering your country.
You need to deport all families, confiscate their property, seize their bank accounts if any member of their families is Islamist or Jihadist.
You need to actively go after Islamists and Jihadists.
That is how you win.
Nice penal system.
Punish the whole family because one family member did something.
I know exactly one nation in the world where such a system exist: north korea.
(And maybe somewhere deep in the african bush or amazon)
But yeah let that day come and some of your family member does some shit. I will be giggling seing your face.