Code - official set of laws or regulations (Dictionary of Law, 3rd ed., Peter Collin Publishing)
Law - body of rules, whether proceeding from formal enactment or from custom, which a particular state or community recognizes as binding on its members or subjects ("law, n.1". OED Online. June 2011. Oxford University Press. http://www.oed.com/view/Entry/106405?rskey=pZFXFp&result=1&isAdvanced=false (accessed August 30, 2011).
Regulation - a rule or order issued by an executive authority or regulatory agency of a government and having the force of law (Merriam's Webster's Dictionary http://www.britannica.com/bps/dictionary?query=regulation) (accessed Sept. 8, 2011)
Rule - regulation or bylaw governing procedure or controlling conduct (Merriam Webster's Dictionary http://www.britannica.com/bps/dictionary?query=rule)(accessed Sept. 8, 2011)
Standard - Simply put, a standard is a documented agreement, established by a consensus of subject matter experts and approved by a recognized body, that provides rules, guidelines or characteristics to ensure that materials, products, processes and services are fit for their purpose. (ANSI definition)