This chapter provides an overview of international law’s limits and opportunities in combating the adverse effects of transport on the environment. It examines these limits and opportunities in turn for international air transport, international shipping, road transport and other regimes which regulate, for instance, the transport of hazardous waste. This chapter thus examines the opportunities and limits of policy instruments in addressing negative environmental impacts arising from transport. It breaks down responses by multilateral, regional and unilateral approaches. Although international law in general does not exclude the possibility of unilateral action, it strongly encourages multilateral approaches. States have considerable freedom to regulate their own vessels and set the rules applicable in their own territory, particularly if they adopt non-discriminatory legislation. Regional initiatives offer several successful models to debate, design and adopt innovative rules which later can find their way into global regimes. Although international regimes on occasion act as constraints on governments’ abilities to regulate activity that is harmful to the environment, the international law provides many opportunities to adopt new instruments to regulate environmental impacts from increased international transport.