Tariff
A tariff is called an optimal tariff if it's set to maximize the welfare of the country imposing the tariff. It is a tariff derived by the intersection between the "trade indifference curve" of that country and the offer curve of another country. In this case, the welfare of the other country grows worse simultaneously, thus the policy is a kind of "beggar thy neighbor policy". If the offer curve of the other country is a line through the origin point, the original country is in the "condition of a small country", so any tariff worsens the welfare of the original country.
Supply management (Canada)
A tariff-rate quota (TRQ) is an international trade policy tool that combines import quotas and tariffs. By 2013, there were approximately 1200 WTO TRQs in the agricultural sector annually among supplying countries under GATT Article XIII. TRQs are a result of the "current market access requirements" and the "minimum market access requirements" forming the basis of the "Uruguay Round country schedules for agriculture." TRQs are two-tiered tariffs in which quotas of certain sensitive domestic products are assigned a quantitative threshold or WTO "minimum access commitments" for imports during a designated time period. Tariffs for imports that are at or below the threshold, are either nonexistent or very low. Imports above the quantitative threshold, are much higher, making the cost of importation intentionally prohibitive. Once imports exceed the "minimum access commitments" as required by the World Trade Organization (WTO), which allow for imports at no or lower tariffs, in Canada imports face prohibitive tariffs such as 168% for eggs, 285% for chicken, 246% for cheese and over 300% for butter. These steep tariffs have been often cited to criticize SM for creating barriers to free trade and artificially raising prices by SM critics such as David E. Bond (2010), Andrew Coyne (2011), Hall Findlay (2012) and President Trump in 2016.