The role of world policeman is a troubling topic, since the debate swings from ultra-militant right-wing "It needs doing, and must be done by the United States of America" to the so-far-leftist-it's-libertarian "We must not meddle in the affairs of other nations, even if this allows for genocide". Now, my phrasing obviously shows my qualms with the opinions, but that doesn't provide much in the way of the solution.
In Why We Fight, the concept of the "One Super-Power World" was mentioned, and the Neocon plan is for America to ensure stability by being the most powerful nation on the face of the other, and keeping it that way. Pax Americana, so to speak. The argument hinges on two points: America is in a position to be the sole superpower, and if America doesn't act on this, America (and the world) will suffer. Post-World War II, another way to avoid a competing-superpowers world was created, and that way was the United nations, complete with its own potential to have military forces.
Military units maintained by a nation, but not kept on standby, could be assigned to the United Nations, ensuring full strength for peacekeeping operations, and maximizing the effectiveness of multi-lateral conflict resolution. This whole point is really just a further footnote to the draft post.
The more important part to expand on was how a draft can limit war.
For the draft to limit war, the whole process of declaring war must be changed, and the definition of war itself must be expanded to encompass police action not undertaken by the UN,
as well as all the other non-wars the US finds itself involved in. For War as occupation of, or conflict with, foreign nations, an army drawn from the populace of the nation engaged in war must be required, and must be willing to do grunt work (and can certainly have options besides that). Quarterly troop surveys must be had, so that politicians can be well aware of the votes that could go against them (absentee voting for the military is good too), and newspapers must publish all congress folks votes on war bills. There is more to be done, but I'm at a loss at the moment.