Solution

Nuclear weapons have limited usage due to arms-control method of cooperation. One of the arms-control treaty was the Nuclear Non-proliferation Treaty (NPT) of 1968 to regulate the acquisition of nuclear weapons. As per this treaty those countries that had fasted and manufactured nuclear weapons before 1967 were allowed to keep their weapons and those that had not done so were to give up the right to acquire them. The NPT did not abolish nuclear weapons rather it limited the number of countries that could have them.