Actually, the situation isn't as clear as one might think. Duels are allowed under two conditions: 1) no "honor duels" (see [1], bottom of page 7) and 2) all participants must be protected (see [1], first paragraph of section 1, page 2). The latter usually means at least protective suits and in most cases dull swords as well.
There has been a duel two weeks ago in Erlangen that violated both these rules [2] - they fought for the honor of their corporation, with sharp swords and without protection. The clusterfuck ended with one minor and one major injury, now police are investigating and politicians are talking about banning duels entirely.
[1] http://www.corpsarchive.de/images/digiarchiv/bghstudnitz.pdf