> (I presume from the language it was a summons he couldn't refuse)
From the article (thanks for linking it btw, it has slightly more info than the English text in the OP):
"This volunteer had no link with that article, having never edited it and not even knowing of its existence before entering the DCRI offices."
So I'm guessing he complied with the summons because he didn't know what it was about and therefore saw no reason not to.
There's some comments below the article you linked, criticizing the sysop for not refusing to delete the article, calling it an abuse of his powers. Well. I don't know who this sysop is, but if he's just an average Jacques, never having had to deal with strong-arming by intelligence agencies, I can totally understand why he chose that course of action. After all, you can always undelete an article, and right then, at that moment, things must have seemed pretty scary to him. From the (English part of the) OP, it states that he tried to talk them out of it, that despite his role as a sysop it was not his decision to make, point them to the Wikimedia Foundation, etc. Who knows what they threatened him with (probably jailtime), I can't blame him for not risking that, or at least not risking it until he gets a clearer picture.
He probably thought, let's get myself out of this first, and let the inevitable publicity shitstorm sort things out later. And indeed, apparently the article is back up.