Earlier quoted context omitted.
Refugees carry little more than their shirts in their travels. Those guns and grenades didn't come with refugees. End of story.
Guns and grenades are not that hard to get, even in Europe. The limiting factor is how many people are willing to lay siege to a concert hall and calmly execute a hundred people, and whether some of those people were let in under the guise of "refugees".
Not hard to get, but when you're talking about dozens of assault rifles, someone somewhere will know what is going where. If your intelligence people are worth their salt, of course.
> whether some of those people were let in under the guise of "refugees".
Yeah, because it's extremely effective to drop your people for months in a Turkish refugee camp, hoping that 1) they will survive in shocking conditions, 2) they will be processed and sent to France, or 3) they will jump on a dinghy and make it to the other side (when chances are that they will just sink), or 4) they will walk through half a dozen borders on high alert and across unsympathetic countries. Pure tactical genius.
More likely, these people had good passports and went through friendly airports smelling of roses. Once on-site, they were armed by existing networks that the French security apparatus still doesn't know how to infiltrate effectively. That's so much easier than leaving people to their own devices across two continents and hope they'll somehow manage to make it to la Gare du Nord at 10 o'clock on Friday morning.