A new EU Reglament has been approved on the 6th of February (2015/187), amending the existing Reglament on the inspection of hand luggage at airports.
In view of new data on the methods used by terrorists to evade the existing procedure to detect explosive devices, brought on airplanes in hand luggage, as of March 1st 2015 the procedures will be amended, to improve detection.
Laptops and other large-sized electronic devices will have to be taken out of the hand luggage to be presented and screened separately, unless the airport in question makes use of the latest generation of explosives detection equipment. So just in case you wonder why on some airports you do have to take out and present your laptop separately, and on some not, this explains it.