A second order optimality condition for multiobjective optimization with a set constraint is
developed; this condition is expressed as the impossibility of nonhomogeneous linear systems.
When the constraint is given in terms of inequalities and equalities, it can be turned into
a John type multipliers rule, using a nonhomogeneous Motzkin Theorem of the Alternative. Adding weak
second order regularity assumptions, Karush, Kuhn-Tucker type conditions are therefore deduced.