There are a couple of issues. This involves trademark issues and gray market goods. Often a company has different licenses in different countries. Formulas change etc. A good example here is Coke. Mexican coke is made differently than US coke. Problems arise when mexican distributors try to export their coke to the US. It begins to compete with US distributors. In the case of Hershey US distrib. say UK distributors are in their territory so an agreement was struck. This is the result. In capitalism, territories are just part of normal contracts. Now how many customers might be unhappy? Well that is something the company will have to consider.

So chocoholics should simply refuse to buy any of Hershey's products. Hershey has disgraced themselves for years by gradually downgrading the products they sell.
When I traveled overseas in the 80's I carried bags of miniature chocolates (American made by Mars) to give to people I met and it was at least as good as chocolate made overseas with a few exceptions (e.g., Belgian.)
Now the US made product is garbage in comparison to the American products made 30 years ago.
Cadbury overseas is better, but it still is a pale competitor to chocolate from Belgium.
For those who have nearby Aldi's and Trader Joes stores, just buy their Belgian imports and compare them to hershey's rubbish. The difference is astounding.
The US products use cheaper materials (e.g., corn syrup) and the result is sub-standard. They are counting on Americans not recognizing the difference out of ignorance.
While I agree that Hershey should defend their contractual rights to manufacture in the US, consumers should vote with their feet and dollars and buy better tasting chocolates.

This looks like another opportunity for an Atlantean company to serve US customers and to remind Hershey of the importance of customer satisfaction and product quality.