Some unfounded claims there. How can you guarantee certain individuals within the UK wouldn't put cost over quality when importing products? Seems a silly claim.
It depends what you mean. If you mean individuals who would import products from overseas that wouldn't meet the UK regulations then this is no different that the situation we're in right now (it's policed by the police). If you mean the UK government would allow cheaper goods into the UK that don't meet EU regulations; and that individuals would try to smuggle these across an open border, then again this is a policing issue. It would be exactly the same as Luxembourg legalising cannabis and it remaining illegal in Belgium... It would not cause a hard border around the perimeter of the former country... It would be policed as a partnership.
This is before even looking at the reality that it would be almost as easy to smuggle products a few hundred metres by boat as it would be across an open border (or a hard border for that matter since very few products are checked anyway). If it were incredibly profitable to smuggle these goods into ROI then it would happen regardless of a hard or open border.
His point is that the definition of a border is the line between different political, legal and regulatory regimes. Control of borders means control of those things. The EU wants to control those things because they want to protect the integrity of the entire cross Europe single market amongst other things. To be honest I expect the answer to your question lies in the difference between the political and legal construction of the EU and the US, ie between nation states pooling trading rules, and a federal system. But I’m not an expert. Possibly the difference also lies in the sheer scales of trade involved (and regulatory alignment needed for that) eg cannabis is an exception for obvious reasons - the rules are still being agreed and trade is quite small overall. But the rules for the vast majority of cross border trade are aligned presumably at federal level, because you the US itself operates a single internal market and customs union. Eg forget cannabis, can chlorinated chicken be legal in California and illegal in Arizona?
My point is that there are dozens of examples throughout the world which involve open borders with different regulatory systems. Likewise there are dozens of examples of open borders with different tax regimes (including the EU itself). Therefore it is disingenuous to say an open border is factually incompatible with different regulatory systems. In fact it's false. Likewise it's disingenuous to state that freedom of movement for working is a non-negotiable aspect of EU membership. There are already restrictions that were brought up in this thread last week on new members such as Croatia, who do not have complete freedom to work in any Nation within the block.
Therefore the EU red lines are just as fallacious and ridiculous as the UK red lines. The only legal requirement is for there
not to be a border between NI and ROI, therefore if both parties set aside their political agendas and made the GFA the starting point irrespective of whether a "deal" can be reached, we'd be much better off.
Supply chains are much more opaque than you realise. Most small retailers will have no clue where their products are actually from (and are unable to verify it in any meaningful way), as they work with wholesalers.
I'm not disputing this, however at some point along the supply chain someone is aware that they're partaking in illegal activity, whether it's importing with the intention to smuggle, or purchasing with the intention to smuggle. Just like we imprison cocaine dealers but punish users to a much lesser extent, we'd put resources into investigating and imprisoning the companies/individuals that were smuggling the goods across the border and merely fine the companies that didn't question the source of their produce, pleading ignorance. Fines as a % of turnover for these companies would make sense (as it would be equitable).