The BWU is a backlit keyboard. This means that you have LEDs that are mounted in holes that go through the switch, and are soldered to the PCB underneath the plate. Also, they will need to be removed from the plate itself, which is also keeping the switch together.
In order to take the top off the switch, you will need to desolder both the switch and the LEDs from the underlying PCB. When you do, make sure you take note of how the LED is wired, as if it's not wired the same way when you resolder it, it won't work.