Sad day for French ATC.
My thoughts to his family.
Some of my colleagues were his classmates.
And how many times have you found a fire door wedged open or such like?
Doors can be left open
inside a tower. The
ouside door to enter the tower is closed and secured.
I don't know about Basel tower, but entry points in CDG, ORY, Paris, Reims and Brest ACCs are secured by Gendarmerie (Military Police) or Air Force. We are checked by humans who compare the picture on the badge and the face of the bearer. They usually know us and are very careful with newcomers.
Once inside the center, doors are automated, the badge becomes the only key. We can see posters everywhere reminding us to check everyone's got a badge.
When a badge is lost or stolen, it is immediately deactivated.
Critical doors (access to control or technical rooms, even some non safety related corridors) will remain closed.