Trade does not need to be "managed"

From today's Open Europe news summary:

Writing in the Telegraph, London Mayor Boris Johnson argues that “It is clear that 25 years ago we made a miscalculation about one of the consequences of EU enlargement. We were right to want to expand the EU… But I think many of us naively and vaguely believed that this enormous expansion would have a beneficial effect on the Brussels imperium… we thought a wider Europe would be looser and shallower – more of a confederal free-trade zone. That is emphatically not what has happened.”

Telegraph: Johnson

There is nothing that a nation can gain from belonging to the the EU that it could not gain by unilaterally adopting free trade. Why is a supra national organization required in order to trade freely with the world? There are no rules required via international agreements in order to "manage" trade.  The market manages trade.  The beneficial consequences of the British repeal of its "Corn Laws" in the mid nineteenth century should have settled this issue for all time.