That's an interesting question when you consider it in terms of terrorism - acts of terror are classified thus because they are against innocent people - but if said people can be held responsible for their government's actions then are they still innocent? For example, one could say that the Americans in the WTC voted for their government, which bin Laden's organisation was 'protesting' against, so therefore they were legitimate targets of attack because they espoused what their government was doing, as opposed to innocent civilians (I don't say this, mind, just making a comment
).
But I think unless you have a true democracy, where every action the government takes is voted on by all the people, then you can't say that the citizens of that nation are responsible for what their government does.