In action seeking declaration under ERISA that plaintiff could properly withhold severance benefits to defendant-employee, where defendant failed to sign restrictive covenant not to compete as condition for receipt of said benefits, Dist. Ct. erred in finding that defendant was entitled to said benefits because formal plan lacked language conditioning severance pay on plaintiff signing restrictive covenant, where Dist. Ct. rejected theory of case that defendant had actually advanced and decided case in defendant’s favor on theory of case that defendant had expressly rejected, without giving plaintiff notice that it was contemplating resolution of case under these circumstances. Moreover, with respect to defendant’s claim that he was entitled to severance benefits pursuant to merger agreement involving his company, as well as terms of subsequent “plan” that implemented said agreement, Dist. Ct. should on remand give parties required notice and then entertain arguments based on language of any post-acquisition plan.