This is a big issue, the root of protectionism vs. free trade.

My first example is the National Energy Program from the 1970s to 1980s in Canada. Left Canada (Alice) legislated the prices Right Canada (Bob) could sell their oil to Alice while the World (Charlie) was offering higher prices.

The second example is a little more convoluted but have a look at the Canada–United States softwood lumber dispute. In this case Bob and Alice are producing newspapers for $5 and $7 respectively. Charlie is a newspaper distributer wants to protect Alice who is his sister, so he charges the buyers an extra $2 for Bob's papers to keep things fair.

Edited for spelling.