The WTO doesn't just limit tariffs, they also restrict what kinds of non-tariff barriers to trade are possible. In very broad terms, countries may still set the

The WTO doesn't just limit tariffs, they also restrict what kinds of non-tariff barriers to trade are possible. In very broad terms, countries may still set their own standards for goods sold there (unlike in the EU), but they must enforce those standards fairly and equally against both local and foreign goods. There's some exemptions for stuff like sanitary and phytosanitary restrictions on animal, plant and food imports, and these will almost certainly cause major problems if Brexit happens, but the WTO certainly isn't just about tariffs. This is one of the big problems I have with the reporting on Brexit, actually. The press not only left widespread misunderstandings like this about the WTO unchallenged, when a politician did finally push back against this all the publications that'd remained silent insisted he was the one pushing dangerous misinformation because people might misunderstand and think the WTO solved everything.