A more thorough explanation:

A civil embargo is a type of embargo that a government imposes on private ships of another nation found in its ports. This can happen during wartime or peacetime, and it is done to force the offending nation to do justice.

For example, during the Gulf War, the United States imposed a civil embargo on Iraq's ships found in its ports. This was done to put pressure on Iraq to comply with international law.

If the civil embargo leads to war, the ships are considered captured. If it leads to peace, the ships are returned to their owners.