Tariff
A tariff is a tax on imports or exports between sovereign states. It is a form of regulation of foreign trade. It is a policy that taxes foreign products to encourage or protect domestic industry. It helps limit trade deficits. The tariff is historically used to protect infant industries and to allow import substitution industrialization.
Eco-Tariffs
One of the major issues that are raised when discussing environmental tariffs, is the issue of a reduction in trade. The argument raised is that tariffs reduce trade and may not actually be targeting the actual source of the pollution. They argue that pollution is not just as a result of imported goods but a large part of pollution suffered occurs within the borders of a country, therefore trade would merely harming trade without actually addressing the root cause effectively.