What if by mandating that you can not spend it at place B results in all of the sister companies of B (C, D, E, F, G, H, I, J, K,) stopping their purchasing from A as a protest.
I'd say that those companies are out of line. They are demanding government waste for their own benefit.
The problem is not necessarily in you equation, it is in the collateral damage that may result by the Government sticking their nose into the market.
The government is another customer buying goods and services in an open market. Why are they not allowed to buy whereever they get the most benefit just like anybody else?
When you tell companies they can not buy goods from Canada, Canadians have the right to reciprocate by not buying goods from the U.S. So you better be very sure that Store A's extra $.50 sent back will cover all them other stores that will lose money due to Canada returning the favor.
Canadians, or anybody else, need to realize that a government doing business with the people that pay it taxes makes sense for that government financially due to the additional taxes those businesses generate. It has the net effect of reducing the total financial outlay. It's not anti-trade, is pro-financial efficiencey and responsibility. The same applies to the Canadian government. That is where any reciprocation should be. It makes sense for everybody.
It is a slippery slope that may or may not work to our advantage! In theory I have no problem with any country buying local, I believe we all should buy local rather than spend away. I believe we should support the local feed store rather than drive 30 miles to save money at another. But passing laws and regulating it can and will have collateral damage!
People need to mellow out and get priorities in order. The government can't spend wisely because of "trade". We can't enact foot safety laws because of "trade" We can't enforce traffic laws because of "trade", states can't have the gambling lawsthe people want because of "trade", etc....., it's rediculous. I'm not anti-trade and I do realize the benefits of trade, but our everyday lives can't revolve on "trade" and "trade" can't be the trump card in every decison that we make.