Video-game publisher Take-Two ( TTWO) is ready to fight back. The company has filed a lawsuit against John "Jack" Thompson, one of its most vocal critics, and a lawyer who has been litigating against Take-Two's allegedly violent game franchises. Thompson has been agitating in Florida to keep Take-Two new releases Grand Theft Auto 4 and Manhunt 2 from being sold to minors; the company's lawsuit seeks to prevent this. Take-Two has said that Thompson's effort to block sales of its games through lawsuits violates the company's First Amendment rights. This is the first time that Take-Two has sued Thompson, who has long spoken out against the content of the company's video games. "This shows the extent to which I have become a problem for them," says Thompson. "Or maybe they are trying to show that I won't be a hindrance in the sales of their upcoming products." Shares of Take-Two were off 5 cents, or 0.24%, to $20.60 in late-afternoon trading Friday. Thompson hit the spotlight when he started rallying against Take-Two when racy content was discovered hidden in its 2004 game Grand Theft Auto: San Andreas. The content became so controversial that Sen. Hillary Clinton asked for legislation limiting sales of video games to minors. Thompson claims he prepped Clinton for the press conference that she had on the issue.