Ambush marketing

Ambush marketing is a form of marketing. Many events, especially in sports have sponsors. These sponsors pay money, which makes it possible to hold the event. In return for this, they get publicity and media coverage. Ambush marketing is a name given to marketing campaigns that are also done around the event, but where no money is paid for the event.
There are many major events where one company will pay money to become the "exclusive sponsor" of the event (or in a category of the event). This blocks other brands or companies. These other brands then seek to promote themselves in connection with the same event. They do not pay the sponsorship fee. Even if they wanted to, they could not, because one brand is the exclusive sponsor. 
Ambush marketing is not illegal, and many people do it. Examples in sport include FIFA World Cup, Olympic Games, and the Super Bowl.
Anti-ambush marketing regulations have become controversial for restricting freedom of speech and self-promotion.