The government is interested in welfare of itself, the state and its resources. If vehicular emissions cause a lot of CO2 emissions and hence climate change, th

The government is interested in welfare of itself, the state and its resources. If vehicular emissions cause a lot of CO2 emissions and hence climate change, the government will want to protect itself, it’s resources and its people. As for making rules or laws - that’s how the government implements such goals or objectives. (This is a slightly broad answer.)