Answer: Secondary boycott
Step-by-step explanation:
From the question, we are informed that the Food King chain stocks products from VitaVeggies at their supermarkets and were recently told by the union to stop purchasing from them even though the union had already told the public and its members to stop purchasing VitaVeggies products.
This is referred to as a secondary boycott. Secondary boycott occurs when a primary boycott had already taken place and the public and other organizations are further told not to buy goods from certain companies.