Abstract This comment on the article by Connolly and Darlington suggests that the experience of SUD-Rail is more ambiguous than these authors assume. Though the union is certainly committed to militant industrial action and to broader social struggles, it is misleading to describe its orientation as 'political'. Its militancy also has two consequences which may prove self-defeating. First, it is unable to appeal to the full range of employees in the French railways. Second, the demands imposed on its activists can prove exhausting and result in 'burn-out'.