I understand ‘we’re not allowed’ completely in a legal way, otherwise he would probably use different and more ambiguous wording.

"Wir dürfen nicht" is very much an ambigous wording in the orignal German. Definitly doesn't imply that there is a legal issue.

And it seems there isn't. In fact, the main legal point here seems to be if providing the weapon can be done by the government or requires a vote from parliament. And it seems it wouldn't even require the vote.

This article goes into details behind the decision. (written by lawyer)