Looks like the domain and hosting are in the Ukraine. This makes chasing after them in a court of law difficult, despite the fact that the Ukraine is a participating member of the Berne Convention.
The best you might be able to hope for is to play on any ignorance they have and write them (and copy their web host) a stern C&D/takedown letter. If they are ignorant of the law, that might do enough to scare them into submission. At the very least it *might* get their web site taken down for awhile. If this is a hobby site, they might then decide it's not worth bothering with.
Good luck. It's always frustrating when things like this happen.