The US is justified in preempting the spread of nuclear arms.

How about a free market in nuclear arms? Buyers and sellers could meet in a comfortable convention atmosphere to make deals. A nifty suitcase nukes might go for a few million dollars, provided costs can be lowered through volume production. Sellers are no more responsible for home their products are used than are manufacturers of knives. Nuclear weapons would go to whomever has fervent well-healed support to pony up the cash.This is a bad idea, because people who have the money to buy nuclear arms do not necessarily have an accompanying sense of responsibility about using them. Fanatics believe that their cause justifies any extreme. Thugs savor opportunities for extortion. The reason we do not currently have a free market for nuclear arms are the strong preemptive measures we have in place, over spearheaded by the US, but with worldwide support. Abandoning the policy of preemption would quickly bring about the market in nuclear arms.1. Self defense justifies preemptionThe justification for preempting the spread of nuclear arms is self-defense. If an enemy attacks with conventional weapons there is a possibility of measured conventional response that can fend off or deter further attacks. A single nuclear strike from a nuclear weapon is so serious that we cannot wait to respond.A 150kT nuclear bomb set off by terrorism at ground level in Manhattan would produce an estimates 830,000 fatalities and 875,000 injuries. [3. http://www.atomicarchive.com...] There would be additional fatalities from fallout and the inability to provide medical care to the injured. " ... it is likely that New York City would never fully recover to its present status as one of the country's leading financial and cultural centers." An air burst detonation would be substantially more destructive.The largest nuclear weapon ever tested was 50 megatons, over 300 times the size of the hypothesised 150 kT terrorist bomb. According to the US National Academy of Engineering, "The primary obstacle to a nuclear attack is limited access to weapon-grade nuclear materials." [4. https://www.nae.edu...] It's also difficult to build an type of nuclear weapon, and especially difficult to build one that is compact and easy to transport. A "suitcase bomb" would be the easiest for terrorists to smuggle into the United States, but a larger weapon could be concealed on board a ship not yet inspected by customs.2. Preemption has workedUS preemption has thus far been successful in preventing nuclear devices from falling into terrorist hands. "The Cooperative Threat Reduction Program (CTR), which is also known as the Nunn–Lugar Cooperative Threat Reduction, is a 1992 law sponsored by Senators Sam Nunn and Richard Lugar. The CTR established a program that gave the U.S. Department of Defense a direct stake in securing loose fissile material inside the since-dissolved USSR. According to Graham Allison, director of Harvard University's Belfer Center for Science and International Affairs, this law is a major reason why not a single nuclear weapon has been discovered outside the control of Russia’s nuclear custodians." [5. Wikipedia referencing http://belfercenter.ksg.harvard.edu... ]Without a doctrine of preemption, there is nothing to effectively prevent the development of a free market in nuclear arms. Currently Pakistan and North Korea possess nuclear arms. in all likelihood they will soon be joined by Iran. Past preemption in Iran included Stuxnet computer virus sabotaging centrifuges to slow the enrichment of uranium. Officials say it slowed Iran's progress towards developing a nuclear weapon by 18 months to two years. [6. http://tinyurl.com...] Current efforts using the threat of continued sanctions are to aimed at keeping Iran at least six months away from bomb construction. [7. http://www.reuters.com... ] That leaves the door open for ultimate preemption.Preemption was ultimately abandoned to allow North Korea and Pakistan to develop nuclear weapons. It's not clear if preemption will be abandoned in the case of Iran. Nonetheless, slowing the spread through preemption has substantially reduced the threat. 3. The spread of nuclear arms risks miscalculationThe threat of retaliation makes it unlikely that any of these three nations would directly attack the US in the near future. However, Iran, Pakistan, and North Korea all have unstable systems of government whereby a new regime could quickly come to power and pose an immediate threat. Supreme Leader Ayatollah Ali Khamenei is noted for extremist rhetoric of Holocaust denial and killing all the Jews. He references "primary jihad" in which the return of the 12th imam presages world annihilation. Khomeini has gone so far as to issue a fatwa in which he authorizes primary jihad without the return of the 12th imam. [8. http://www.wnd.com...]North Korea's Kim recently executed his uncle, with the "shocking public purge of Jang as a sign of instability in Kim Jong Un's leadership." [9. http://articles.latimes.com...] Secretary of State Kerry said, “It tells us a lot about, first of all, how ruthless and reckless he is. And it also tells us a lot about how insecure he is, to a certain degree,” In 2009, "President Barack Obama said the government in Pakistan is “very fragile” and expressed concern about security in the nuclear-armed nation, as Pakistani forces battled Taliban militants in the northwest." [10. http://www.bloomberg.com...] Since then, the country has held on an accomplished a peaceful transition of government. With the US withdrawal from Afghanistan, there will be renewed pressure to ally with terrorists taking over the region. The direct threat from established governments lies in a miscalculation from an extremist leader. For example, radical leadership in Iran might assume that a first strike on Israel could be successfully accomplished without the U.S. retaliating. North Korea has made a business of extortion:For almost two decades, North Korea's Kim dynasty ran a reasonably successful extortion racket based on the theory that South Korean, Japanese and American leaders would appease the hereditary dictatorship rather than accept the material, moral and global economic risks a war in East Asia entails. The Kim mob's crude bargain has been, "Give us food and fuel, and we won't kill a bunch of people." [11. http://tinyurl.com...]An extremist regime may risk use against a US ally, believing the US will not intervene.4. Nuclear proliferation diffuses responsibilityThe greater threat is probably from providing nuclear arms to terrorist organizations. Iran might provide nuclear weapons to the terrorist Hamas, to whom it provides financial support. http://www.timesofisrael.com... they could do this with a story that Hamas needs to deter an Israeli strike. Additional steps could be taken to distance Iran from Hamas potential use of the weapons, such as signing a treaty prohibiting use. Hamas could claim that the weapon was stolen by an even more extreme organization.Currently about 40 nations have the technical ability to manufacture nuclear weapons. [12. http://www.rense.com...] If preemption is abandoned, we can expect Saudi Arabia to be among the first to add nuclear weapons. The BBC reports that weapons are ready to be shipped from Pakistan, in a move that would start the free market in these weapons. [13. http://tinyurl.com...]As more nations have weapons, the probability of one falling into terrorist hands, either directly or through a country that claims plausible deniability. A strong policy of preemption is justified to forestall this threat.