Originally Posted by
MSPeconomist
IIRC there was a German court decision saying that this is not enforceable and flight coupons can be used in any order (although I don't understand how this would work with inflexible tickets). It doesn't seem to apply to the entire EU but might be applicable if your itinerary touches Germany, if you have a German address, or if the tickets were issued in Germany. IANAL.
The LH website now seems to allow you to choose whether you'd like a ticket that can be used out of sequence in a similar way the BA site allows you to choose whether you'd like flexibility. I've not had time to draw comparisons on the fares being quoted there but I'd be as bold as to suggest opting for a ticket that can be used out of sequence will cost more than one that cannot.