Any employee can file a lawsuit for any reason. But filing and winning are two different things.
Most lawsuits end up dismissed after the employer shows the court it followed its own rules and fairly disciplined the employee.
Recent case: Mary Haggins, who is black, worked for the Carolinas Medical Center as a technician. She was often late for work, and the center had strict rules that required discipline for employees who were late more than 10 times per year. Haggins was late 22 times in one year, was warned and then fired as the policy required.
She sued, alleging discrimination. But she couldn’t point to a single other employee of any race who had come close to her tardiness record. The court dismissed the case. (Haggins v. Carolinas Medical Center, No. 3:09-CV-78, WD NC, 2010)