This paper discusses the moral justification behind placing a tax on foods in correlation with their greenhouse gas emissions. The background is a report from 2016 by the Danish Council of Ethics promoting a national tax on the consumption of meat from ruminants as an initial step to curb the 19–29% of total anthropogenic greenhouse gas (GHG) emissions stemming from the food sector. The paper describes the contribution of food production and consumption to climate change and how a change in diet, away from ruminant meat in particular, could lead to substantial reductions in GHG emissions from food production and consumption. We discuss whether, given the anticipated effects on humans and the nature of climate change, individual consumers have a moral responsibility to change their diet and/or whether governments are justified in restricting the individual consumer’s freedom of choice through taxation in order to effectively reduce emissions. The paper concludes that such an intervention is warranted and necessary, both from an efficiency perspective and from an ethical perspective.