TheOptimizationIdiot - 3:22 am on May 8, 2013 (gmt 0)
The solution you need probably falls more in the area of a DMCA take down request, either tho their ISP or to Google.
I agree, but would add, if it's not a proxy according to w3 standards and you file a DMCA, make sure you get the wording correct, because if you say it's a proxy, even a non-transparent proxy, neither Google nor the host will legally be able to uphold the DMCA take-down request, to the best of my knowledge.
Non-transparent proxies are a PITA, but if it's really a proxy according to w3 standards, then they are requesting the pages dynamically on behalf of their users and you can block them from doing so via .htaccess so there's no need for a DMCA complaint to be filed, just block them, because if it's a non-transparent proxy a DMCA will in all likelihood and (again) to the best of my knowledge, not be honored by the host or Google.
Google spidering, caching and showing pages from non-transparent proxies in the results and how I feel about it is another story for another thread. The short version is: I don't like or agree with it. That's not the point right now though, getting your site back where it should be is.