We will ban all militaries! Ban war!
Of course, without a military, such a ban cannot be enforced.
I believe that idea was tried already. The treaty of Versailles made it illegal for Germany to have a military beyond a small self defense force.
When Germany violated the treaty, the French and British did nothing. This treaty had clearly stated what Germany’s navy should be – no submarines and only six warships over 10,000 tons. In June 1935 the Anglo-German Naval Agreement was signed. This allowed Germany to have one third of the tonnage of the British navy’s surface fleet (probably the largest in the world at this time) and an equal tonnage of submarines.
Why did Britain agree that Nazi Germany could break the terms of Versailles?
This event saw the start of what was to be called appeasement. It was believed that Nazi Germany would develop her navy regardless and that an official agreement between Nazi Germany and Britain would do much to foster relations between both countries. No one was willing to use force to back up the agreement.
That is a universal truth: those who are unwilling to use force in self defense will always be the victims of those who are willing to use force to obtain what they want.
To have peace, be ready for war.