Not a "Button" in the sense of something fitting in a buttonhole to hold a garment together, though it may be made to fit in a lapel buttonhole. But most of them now are in the form of small pin-on badges usually worn on the chest. I have one saying "Nej til EU" (No to the EU) which I bought in Norway. You can't buy buttons protesting against the EU in the UK, probably because of some EU regulation!