Last week, in Magnetar Tech. Corp v. Six Flags Theme Parks, Inc., C.A. No. 07-127-LPS (D. Del. Feb. 18, 2011), Judge Stark denied a motion by some of the defendants to amend their complaint to add an antitrust counterclaim under the Section 2 of the Sherman Act. The opinion is brief and interesting. It explains the high bar for factual allegations when asserting an antitrust claim, and distinguishes such claims from the easier-to-prove inequitable conduct claims. Here, Judge Stark found that defendants had failed to meet that high bar, and denied the motion to amend.