Does govt. have a website setting regulations...or standard of identity... as to how to determine your race?

Question

For instance...Barack Obama has african-american father and Caucasian mother...he claims to be african-american. Isn't he just as caucasian as he is African-American... 50/50? Tiger Woods has an African-American father and a Phillipino mother...he claims to be African-American. Isn't he also just as Phillipino as he is African-American? When Tiger and his caucasian wife have children will they be African-American or caucasian?
I have Native American in my family -tree. How much native-american ancestry do I need in order to claim that I am Native-American? Does my Great-grand mother count? Is that enough? Has the government written a standard of identity for each race? As races continue to intermix how does one know what to claim themselves?
Where is the standard of identity?

Answer 1

The one-drop rule was the standard used by the government to determan who's black. So according to this, Barack Obama, Tiger and others like them are not white, but black.

http://www.pbs.org/wgbh/pages/frontline/shows/jefferson/mixed/onedrop.html

Answer 2

You could try the Census Bureau, but I think they mostly rely on your own view of your identity.