"This is War"
Declared Senator Ted Cruz, as he hurried back to Washington to introduce a declaration of war in Congress. OK, he didn't really do that latter stuff, he just spouted some inflammatory but otherwise meaningless rhetoric. He wants police patrols of "Muslim neighborhoods" in the US to make sure that they get radicalized. What a dumb-ass. And he's only the second scariest guy running for President.
Meanwhile, in Belgium, where there already are lots of radicalized Muslims, they are forced to ponder the consequences. When Ulysses Grant was President, at one point the Ku Klux Klan had become such a grave threat (in his opinion) that he suspended habeas corpus, one of the key legal rights of Americans. That and other firm tactics rapidly destroyed the Klan and it didn't rise again until D.W. Griffith's propaganda masterpiece, The Birth of a Nation resuscitated it many decades later.
Suppose Belgium is prepared to take similarly draconian measures, suspending many civil rights in an attempt to control its terrorism problem. Would that help? Would mass expulsions do the trick? One critical problem is that most half-way measures exacerbate the problem. Brutal repression would likely change hundreds or thousands of radicalized Muslims into tens or hundreds of thousands.
One obvious measure which would likely have few of these side effects is for Europe and the US to unite to crush the Islamic State. I really can't comprehend why we suffer it to continue to exist.