Whatever the text says, the courts have always ruled that they are.
Just as the courts will rule when the United Nations decides to impose its own explicit tax on American citizens (in addition to the current indirect tax collected by the federal government to fund UN activities).
Probably because the 16th Amendment to the US Constitution overrides Title 26.
http://www.law.cornell.edu/uscode/26/usc_sec_26_00000001——000-.html
The Table 26 ‘out’ is a myth.
http://docs.law.gwu.edu/facweb/jsiegel/Personal/taxes/JustNoLaw.htm
I hope no one goes to jail over the bad advice in this article.