Economic sanctions are useful in sending a message to a country, especially when that message is spoken by a collection of countries. During apartheid in South Africa, sanctions were enforced by the United Nations starting as early as 1962. In 1985, Britain enforced sanctions on South Africa, and a year later the U.S. passed the Comprehensive Anti-Apartheid Act. This act enforced sanctions on South Africa in an effort to move the country out of apartheid. These countries stopped purchasing uranium and other products from South Africa, and the collective decision to do so devastated the South African economy. In addition to their effect on the economy, the sanctions helped to end apartheid. Sanctions, when enforced by a collection of diverse countries, are highly effective.
Some economic sanctions simply are too political to be effective, even when enforced by a collection of countries. For example, during the Cold War, sanctions were mostly ineffective. This is because if the U.S. and anti-Communist countries refused to trade with a given country the USSR would take their place, and vice versa. When there are multiple "superpower" countries with different ideologies, sanctions become significantly less effective.
[P1] Countries who impose economic sanctions have an economic relationship with the target country that would be negatively impacted by limiting or ceasing trade. [P2] Therefore, economic sanctions are an effective non-violent penalty to a given country.
Rejecting the premises
[Rejecting P1] Not all countries are dependent on each other and/or economically intertwined.