So it happens that labour law scholars are forced to familiarize themselves with old and new economic concepts and models, in order to draw from them the arguments – indispensable also from the strictly juridical point of view – for the defence of labour law as an effective means of social justice, of effective guarantee for the weakest workers, of correction of major labour market failures. I recall only the most important and well-known concepts and models that are commonly opposed to the insider/ outsider theories[2]: