There's no sane universe in which a Prime Ministerial candidate should grilled on sub-paragraphs of the GATT by @afneil. None.
Question: "Is there a WTO legal way the UK and EU could mutually agree not to charge tariffs on one another's products?"
Answer: "Yes there is and it's called a Free Trade Agreement."
That's it. No paragraphs. No legalese.
Question: "Is the EU going to agree to something like that?"
Answer: "They'd have extended existing arrangements under the WA and negotiated towards something like this, but have said they won't do so on Day 1 of No-Deal."
Unlike the UK, which has held tariff imposition up to be of totemic importance, the EU has consistently recalled that while No-Deal tariffs are A problem, they're not THE problem.
They deliberately and maliciously broke the discourse.
The EU asked the UK not to waste this time.
I hope the charlatans are proud.