Same occurs with nations. Small nations joins together to form large collection of nations, voting democratically on rules and decisions. EU is an union of European countries. If a country want to be in EU they will have to follow the decisions on the democratic process. We can eval this further and say that independent individuals can choose to form nations, and those independent nations can choose to form unions, and those unions can form global trade agreements, each however limited to the democratic process which dictate conditions, rules and laws.
Individuals can also choose to leave their countries, countries can leave unions, and unions can leave the global trade agreements. It is a choice. They do however loose the ability to achieve those things that is only possible when people work together.
Calling sanctions war is like calling boycotts theft. Vegetarians are not stealing money from beef producers.
What boycotts and sanctions can be is passive aggressiveness. It harms people on a social level, and since humans are social creatures, it feel like violence. The problem of comparing violence with social violence is that not being invited to a party hurt, but it hurts in a different way from getting knifed. Our brain interpret social pain as physical phantom pain, but we must be able to distinguish between real and non-real pain. Society depend on it.
The reason blocking a port is a act of war is that the nation blocking that port is also blocking it for other nations who might be willing to trade. That is like a vegetarian going out during the night and killing off the beef productions herd of cows.