Cost of living 5. Growth and jobs 8. One of the lessons of the protectionism that dominated the early decades of the 20th Century was the damage that can be caused if narrow sectoral interests gain an unbalanced share of political influence. The result was increasingly restrictive policy which turned into a trade war that no one won and everyone lost. Superficially, restricting imports looks like an effective way of supporting an economic sector.
Protectionism can also escalate as other countries retaliate by raising their own trade barriers.
That's exactly what happened in the 1920s and 30s with disastrous effects. Even the sectors demanding protection ended up losing. Governments need to be armed against pressure from narrow interest groups, and the WTO system can help. The GATT-WTO system covers a wide range of sectors. Governments do just that, regularly.