Hawthorn's claim for interference with his right to severance benefits arises under ERISA, which governs the Plan. ERISA prohibits an employer from discharging a participant in an employee benefit plan for the purpose of interfering with the attainment of any right to which the participant may become entitled under the plan. 29 U.S.C. §1140.... Hawthorn attempts, but fails, to establish pretext[.]