A lawsuit triggered by the hostile takeover attempt of Casey’s General Stores Inc. was dismissed last week in U.S. District Court in Des Moines. Casey’s had alleged that Alimentation Couche-Tard Inc. of Canada violated federal securities law shortly after it announced it was attempting to buy the Ankeny-based convenience store operator. Couche-Tard countered that a state law Casey’s used to fend off the takeover was unconstitutional. Couche-Tard dropped its tender offer on Sept. 30, a week after Casey’s shareholders cast an overwhelming vote of approval for the company’s board of directors and rejected a slate of candidates offered by Couche-Tard.