Paternalism means, roughly, benevolent interference - benevolent because it aims at promoting or protecting a person's good, and interference because it restricts a person's liberty without his consent. The paternalist believes herself superior in that she can secure some benefit for the person that he himself will not secure. Paternalism is opposed by the liberal tradition, at least when it targets sufficiently voluntary behavior. In legal contexts, policies may be paternalistic for some and not for others, forcing trade-offs. In medical contexts, paternalism can be an open or hidden aspect of the relationship between caregiver and patient.

Drink driving causes great suffering and material destruction. The alcohol interlock promises to eradicate this problem by technological design. Traditional counter-measures to drink driving such as policing and punishment and information campaigns have proven insufficient. Extensive policing is expensive and intrusive. Severe punishment is disproportionate to the risks created in most single cases. If the interlock becomes inexpensive and convenient enough, and if there are no convincing moral objections to the device, it may prove the only feasible as well as the only justifiable solution to the problem of drink driving. A policy of universal alcohol interlocks, in all cars, has been proposed by several political parties in Sweden and is supported by the National Road Administration and the 2006 Alcohol Interlock Commission. This article assesses two possible moral objections to a policy of universal interlocks: (i) that it displaces the responsibility of individual drivers and (ii) that it constitutes a paternalistic interference with drivers. The first objection is found unconvincing, while the second has only limited bite and may be neutralized if paternalism is accepted for the sake of greater net liberty. Given the expected technological development, the proposed policy seems a commendable health promotion measure for the near future.