One of the many absurd Project Fear scares is that we will be unable to export many goods to the EU without an Agreement because they will say they do not comply with EU rules any more once we have left. This flies in the face of the fact that they will still so comply, as the companies exporting will continue to meet EU specs for EU trade.
More importantly, the EU has built World Trade rules into its own legal structures. The WTO, for example, has a Technical Barriers to Trade Agreement to deal with just such issues, and a Sanitary and Phytosanitary Agreement for agriculture. These require a WTO state to accept product from another WTO state as complying with standards unless there is an objective reason to establish they do not comply. The EU has and uses powers to recognise the standards and competent authorities of third countries to be able to import their goods and to comply with its WTO obligations.
So hear this all you Project Fearmongers. The EU is a legal construct which also has to live by the rule of international law. Under WTO rules non tariff barriers have been dealt with, so the EU cannot legally mount a Napoleonic blockade against UK goods once we have left. After all, the day following our departure UK produce and products still meet all existing EU standards. I still find it odd that those who most love the EU think the EU would want to try to do this. It would also, of course, be a violation of the EU Treaties themselves which require the EU to develop positive relationships with neighbouring states and to promote trade with them.
The WTO has done good work in recent years to make it illegal for countries to impose new non tariff barriers to impede trade. The EU has built these requirements into its own law codes. People on both sides of the Channel will continue to honour contracts and buy and sell to each other after our exit. To suggest otherwise is silly scaremongering.