An aerodrome, airport etc. is a place from which an aircraft normally takes off and lands. If the owner of the aerodrome/airport closes it, for that time period, it is no longer a place where an aircraft takes off and lands - by the owner's direction. So don't land and take off there. If a store is closed, you don't break in and take what you want anyway do you?
If you have an emergency situation, a "closed" aerodrome could be a forced landing site, and if you do a good job, the aircraft could be flown out again. If a maintenance reason has caused you to decide to land, in flight you have declared the aircraft no longer airworthy. So, once on the ground, how would you declare the aircraft airworthy again to take off? You're not going to take off an unairworthy aircraft from a closed aerodrome are you?
There are airports I know of in the US, which were well declared closed. Pilots landed anyway. They found zero sympathy, and were told that the airplane would have to be disassembled, and trucked out = expensive.
And read your insurance, it probably has exclusions about operations from non or closed aerodromes.
This is the information age - you can't say you didn't know that you should not operate from any given place!