Why ever not? The fact that they will offer to sell some goods that you don't wish to buy does not mean they can insist on you buying them

That is a very weak argument Nigel. We have agreed standards on animal welfare and food quality. We might choose to change them of course, but at the moment they are what they are. The idea we can just import things that breach these standards and leave it up to people to choose what they like would apply to any sort of regulation at all. Why insist electrical goods are safe? Let them go into the shops and people can choose not to buy them. Why not allow lead painted toys alongside safe ones?

The standards are what they are. If the country, via its government, changes them fine. Until then, nothing breaching the standards should be admitted.

There is a very strong opposition to lowering food standards, as far as polls can be trusted. The government is currently pledging not to lower the food standards, If it then chose to do so without consulting in any way such as via a manifesto, it would have created yet another reason to vote against it.