Actually, Art24 is not "obscure". Everyone uses it.
It's the *interim* version that's obscure.
@MalmstromEU has now rubbished the idea that the EU will agree quickly to a simple one, while it negotiates a final one with the UK.
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By @tgemiles
It's the WTO rule governing all free trade agreements in goods, including the EU Customs Union.
The WTO's database lists 264 currently-active agreements all over the world that have been notified under GATT Art24.
rtais.wto.org
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It's the transition in the Withdrawal Agreement, just not specified as an "interim" one under Art24.
And then there's the backstop, which probably isn't even short-term