This is very good. @hilarybennmp, for the opening paragraph.
A couple of additional and important points.
First, it is critical to note that the Joint Committee’s role and powers under Art 5 relate only to *duties*: that is to say which NI imports from GB fall within what is really an exception to the “EU duties payable” default.
The JC has *no* role in determining or modifying the customs *checks* that apply on such imports: so it cannot modify the application of all the rules on checks set out in the Union Customs Code (which is fully applicable to *all* NI imports from outside the EU: ie from GB).
Second, and importantly, if the JC fails to agree on the scope of the “no risk of circulation to the EU” exception, my reading of Art 5 is that the scope of that exception is then 0: everything is treated as subject to EU duties. That rather affects the negotiating dynamics.
Finally, the “JC can deal with this” line was trotted out equally unconvincingly in a reply to @SKinnock about Article 10 (State aid).
