The claim is that s. 47.1 of the Canadian Wheat Board Act bars the abolition of the Board without approval from farmers.
I think such approval ought to be obtained -- but legally I don't see it is necessary. By my reading of the section approval is needed to change the commodities sold by the board under its monopoly, not to abolish the existence of the board itself.
Anyway, here's the section and you can decide for yourself:
Canadian Wheat Board Act
47.1 The Minister shall not cause to be introduced in Parliament a bill that would exclude any kind, type, class or grade of wheat or barley, or wheat or barley produced in any area in Canada, from the provisions of Part IV, either in whole or in part, or generally, or for any period, or that would extend the application of Part III or Part IV or both Parts III and IV to any other grain, unless
(a) the Minister has consulted with the board about the exclusion or extension; and
(b) the producers of the grain have voted in favour of the exclusion or extension, the voting process having been determined by the Minister.