The person in the window seat usually has control over whether the window shade is open or closed. However courtesy plays a role too. On overnight flights across time zones window shades should be closed whenever possible – many passengers are trying to sleep, but it may be light out early. The outside light might also interfere with an aisle seat passenger seeing their laptop screen and getting work done.
Reasonable requests should be accommodated, though it’s up to the passenger in the window to make the trade-off decision. One key to peace on board is good communication.