Particular types of trade barriers cause additional damage because they provide opportunities for corruption and other forms of bad government.
One kind of trade barrier that the WTO’s rules try to tackle is the quota, for example restricting imports or exports to no more than a specific amount each year.
Because quotas limit supply, they artificially raise prices, creating abnormally large profits (economists talk about “quota rent”). That profit can be used to influence policies because more money is available for lobbying.
It can also provide opportunities for corruption, for example in the allocation of quotas among traders. There are plenty of cases where that has happened around the world.
In other words, quotas are a particularly bad way of restricting trade. Governments have agreed through the WTO’s rules that their use should be discouraged.
Nevertheless, quotas of various types remain in use in most countries, and governments argue strongly that they are needed. But they are controlled by WTO agreements and there are commitments to reduce or eliminate many of them, particularly in textiles.
Many other areas of the WTO’s agreements can also help reduce corruption and bad government.
Transparency (such as making available to the public all information on trade regulations), other aspects of “trade facilitation”, clearer criteria for regulations dealing with the safety and standards of products, and non-discrimination also help by reducing the scope for arbitrary decision-making and cheating.
Quite often, governments use the WTO as a welcome external constraint on their policies: “we can’t do this because it would violate the WTO agreements”.