When the U.S. Department of Justice shut down MegaUpload and sued its operators for copyright infringement last week, users who were storing files legally on the site became collateral damage. Now, some of them are looking to sue the government over lost data, TorrentFreak reports.The counterattack is being led by the Pirates of Catalonia in collaboration with Pirate Parties International--overseas political groups who oppose harsh laws against copyright infringement."The widespread damage caused by the sudden closure of Megaupload is unjustified and completely disproportionate to the aim intended," a posting on the Pirates of Catalonia Website says. The group has created a form where users can register their complaints, and plans to "facilitate submission of complaints against the US authorities in as many countries as possible, to ensure a positive and just result."At the moment, however, it's not clear what legal basis users might have for lawsuits. The only specific statutes the Pirates of Catalonia mention are Articles 197 and 198 in the Spanish Penal Code, which govern the misappropriation of personal data. Other than that, the group only says it is investigating "potential breaches of law."Furthermore, Megaupload's terms of service stated that users who stored data on the site did so at their own risk, so users may have a tough time arguing that the U.S. government is liable for lost data. (Most online file sharing sites cover themselves in this manner, which is why putting all your eggs in one online basket isn't a great idea.) Filing complaints may be comforting for MegaUpload's former users, but doing so isn't likely to help return what was lost.Follow Jared on Twitter, Facebook or Google+ for even more tech news and commentary.