I generally check my skates when I travel to Europe, just because it's easier than hauling them through airports. When I went to England in December though, my checked bag was too heavy with the skates inside so I packed them in my carry on. I put the plastic guards on and then added big, fluffy blade overs over those as padding. With great trepidation I watched the TSA people scan the bag; one young agent called her supervisior over to verify what she saw, the supervisor just shrugged and said, "They're ice skates." and let them pass. I heaved a great sigh of relief.
On the way home, though, I put the skates in checked baggage. I don't need the stress.
If you're hopping around different countries in Europe, though, I'd check with the various airlines. The baggage requirements vary. I've never had a problem with skates in my checked bag but I haven't tried to carry them on on flights within Europe either.