Originally Posted by
televisor
I'm about 90% certain that it's an aviation authority specific thing. The FAA allows anything that doesn't protrude from under a seat. European and Asian AAs don't allow any bags at all, presumably because they can and will move in the event of a mishap.
Nothing at all to do with policing sizes, everything to do with safety regulations being country specific.
Yes - I found that out when flying on LH. The person in the seat next to me was shocked that I tried to put my laptop under the seat in an exit row. Seemed to be an EASA thing.