  In this paper we study constraint qualifications and optimality conditions
for bilevel programming problems. We strive to derive checkable constraint
qualifications in terms of problem data and applicable optimality conditions.
For the bilevel program with convex lower level program we discuss drawbacks of
reformulating a bilevel programming problem by the mathematical program with
complementarity constraints and present a new sharp necessary optimality
condition for the reformulation by the mathematical program with a generalized
equation constraint. For the bilevel program with a nonconvex lower level
program we propose a relaxed constant positive linear dependence (RCPLD)
condition for the combined program.
