It also depends upon whether the decals have been clear-coated over. In which case, you won't be able to get them off without damaging the top layer of clear paint.

Look carefully at the edge of the decal, is it sharp with a square edge you can catch with your finger? If so, it's a sticker and you can peel it off.

However, if the edge is smooth with a layer of paint over it, it's probably a decal that's been painted over and will be difficult to remove.