Protectionist measures may provoke retaliation.

If foreign governments do retaliate by imposing their own trade restrictions then, while the country’s imports may fall, so might its exports. International trade would decline and again global output would fall.

Protecting jobs argument

Arguments in favour of trade barriers and taxes on imports, on the grounds that these policies benefit citizens and prevent jobs from being exported, tend not to be good arguments.

The problem is that their arguments consider only the benefits of protectionism without also considering the cost. Trade barriers and taxes on imports do protect the specific jobs that they’re intended to protect. However, other jobs are often sacrificed in the process.

Protects an unproductive industry

Protecting an unproductive industry that faces foreign competition only allows it to keep using resources that would be better used by more vibrant industries.

Workers who would otherwise move to jobs in innovative, highly productive new industries instead get stuck in an industry so unproductive that it can survive only by having the government rig the economy in its favour