Unilateral pricing policy is the result of B&M stores pressuring manufacturers to set price floors.
My take on it? It may not be illegal, but it is inefficient for the market. It's essentially punishing larger camera stores like Amazon and B&H (which is itself not that large) because they are more efficient and can pass on their lower overhead costs as savings to consumers.
I've stopped buying at big box stores like Best Buy because of their high prices and bad service. I've also had better service buying from Amazon and B&H than the local camera shops (who often price higher than minimum price anyway), so UPP is not going to make me more likely to buy from them. It will, however, make me less likely to buy camera gear in general, given the prices Canon is asking.