Official position of both Académie française and Office québécois de la langue française is that accents must be preserved in capital letters. However, it is common in France to drop them, while they are almost always preserved in Québéc. I have heard that the reason is that European French keyboard layout makes it difficult to type accented capital letters, unlike Québécois French layout which makes writing them easy. But I am not sure if this is the cause rather than the effect of the practice.