It wasn't mentioned in the article in the Guardian, but I wonder if it has anything to do with TTIP.
British farm standards at the moment are much higher than US ones. That's one of the reasons that MEPs want us to stay in Europe and fight against TTIP.
If TTIP is passed, American companies will be able to sue the UK for not importing foods with GM, or other foods that do not adhere to our standards. Not that all British ones do, as you will see if you go on the www.viva.org.uk website, but at least we can prosecute those companies that break the law at the moment.