No-deal Brexit: What would be the basis for a WTO complaint if goods entering Ireland are checked at Dunkirk?

Question

There's a BBC article which goes over several scenarios in case of no-deal Brexit containing the following paragraph:

It is possible that if EU authorities decide not to check UK goods at the Irish border, but do check them at Calais or Dunkirk, it would provoke a complaint to the WTO.

The WTO matter is not elaborated any further in that article. So what would be the legal basis for such complaint? Is it stated in the WTO treaties somewhere that goods must be checked (right) at the border if they are checked at all?

Answer 1

WTO rules require countries to charge everyone the same tariff, so any trade operating under WTO rules must abide by that. If checks were only done at Calais/Dunkirk but not along the Irish border, trade between the EU and UK would be governed by WTO rules but tariffs would not be levied on all goods traded (i.e. the ones crossing the Irish land border).

This would prompt complaints from other WTO members because it gives the UK unfair tariff free access to the lucrative EU market.

The UK has proposed creating a new high tech system to do the border checks away from the physical border, using some kind of electronic system. It's unclear how this would work as no such system exists anywhere else, or how it would prevent smuggling. In any case such a system could not be set up by March 29th 2019 when the UK leaves the EU, and probably not for many years afterwards.