Are there practical reasons for states – even the most powerful ones -- to allow limits to their power?
While many argue that Thucydides was a political “realist,” emphasizing the importance of power and military force, immediately following the Melian Dialogue, he begins the story of Athens’ downfall. In the end, its absolute power destroys it.
Lord Acton famously said:
Power corrupts, and absolute power corrupts absolutely.
Thus the first reason a state might want to limit its own power has to do with the knowledge that by limiting the amounts of power one has, one limits possible abuses. Just as, for example, most countries try to put in place political systems of checks and balances to avoid being subject to dictators and tyrants (think of the Athenian system of ostracism), so too states can voluntarily, for example, give up imperial possession and cede powers to international organizations.
Another reasons states give up power is to encourage reciprocity. International organizations, such as NATO, the EU, the International Criminal Court, the WTO, and other similar groups provide forums in which all members agree to abide by international standards rather than making decisions unilaterally. Thus nations may agree to reduce their own nuclear arsenals in concert with other nations dong the same to the benefit of all.