They seem to be quite effective here in Norway. We have very high rates on imported food that competes with local production. The goal is to ensure we can be fairly self-sufficient when it comes to food.

So far it seems to be doing a good job at keeping cheap EU-made food out of our grocery stores.

Of course implementation matters a lot. We have no farmers growing corn in Norway, so we don't have any tariffs on corn. We do have farmers growing apples, but there's no harvesting those during our snowy winters so our tariffs on apples are just active when local apples are in season. We do produce beef all year, but not always enough so they hand out limited quotas allowing for massive reduction in duties to compensate and meet demand.