And the country of registration plate or sticker on the rear.
This is the problem with laws. As soon as they are relaxed a little, some people think they can take liberties.
It is not about this, of course there are laws. Some obey, others try and get around them (like me). I was looking advice, for what its worth I think police on UK mainland are stricter than NI, and the plates I see daily in NI that fail to conform even in ways you could not imagine, drive fine.
My point was with a simple flag and small fingernail slogan. I will go ahead with the slogan and forget about flag. Having a sticker is not the most robust way to enforce such laws, and ones apparently serious, which is why temp measures like this exist. E.g driving over granny, peel sticker off, drive!