In the context of a homogenous good industry with Cournot rivalry and technological asymmetries among firms, equally skilled workers can be grouped according to their different reservation wages. Under decentralized firm-union bargaining, we show that unions may offer to firms the option to discriminate wages across such groups of employees and, by that, to achieve cost sub-additivity in the equilibrium. We subsequently propose that to combat the emerging wage discrimination a benevolent policy maker may activate either taxation, or subsidization, policy. Interestingly, while the former policy always entails a welfare loss, a welfare gain may emerge under the latter policy, relative to the no policy-wage discrimination status quo. Thus our findings suggest that the E.U- antidiscrimination directives may prove to be effective on both egalitarian and efficiency grounds.