The UCI has released new guidance concerning Article 1.3.014 on what they are, rather wonderfully, calling the "horizontality" of the saddle.
From the 1st of March 2012 checks on the "horizontality" of the saddle will be conducted at WorldTour events, World Cup events and World Championships for the road, track and cyclo-cross.
The UCI have produced a guidance document covering this issue, so if you're undecided where you stand (or indeed which way to lean) on the subject of horizontality, check out the details her: Horizontality Download (Word file)