I was wondering about that too. But this is not an official blog, and he seems to do this as a privat person, so I guess the law does not apply. However, if you check, you will see that the information on official website of his department is in four languages.

If the law would apply he not only would have to write his blog in German and French, but also in Italian, not to talk of the Romantsch. Guess that is asking a bit much. :-)