Faced with the inaction of liberal democracies to effectively tackle global warming, many climate activists engage in forms of protests that involve committing minor criminal offences. They seek to shape official decisions on climate policies by resorting to civil disobedience. Some of these activists, rather than accepting punishment, have successfully claimed to be acting in a justified manner by invoking the necessity defence. The aim of this article is to show that, within the framework of representative democracies guided by the rule of law, the climate necessity defence must be rejected, since such protests do not meet the ‘non-legal alternatives’ requirement. This does not mean, however, that protesters should be punished as common offenders. Their acceptance of responsibility and political motivation should be taken into account as a mitigating factor at sentencing.