Reasonably sure, yeah. Not only am I somewhat sure that you can indeed always tell by the packaging (at least here in Germany), I also check the list of companies every 6 to 12 months.
And yeah, the most boycotted company (assuming it is true) means there is barely any effect. People don't boycott, many people don't even care enough to talk, far fewer want to walk.
I'm glad it is easier to tell there. In the US there are no such requirements :(. I've noticed looking at web sites of various companies that there seems to be some basic disclosure requirements in some EU countries that are helpful (like a contact address, which many companies don't have on their website in most of the world).