Q. How do I cite the Constitution of the World Health Organiztion (WHO) using APA?

Chapter 11 in APA's Publication Manual discusses legal references, including laws, regulations, and constitutions. Section 11.9 (pp. 366-368) has the rules for citing constitutions and similar documents.

If you are citing the entire constitution, all you need to do is to name it in your text. You do not need a formal citation or reference. If you do choose to cite the entire Consitution, the citation would look like this:

World Health Organization (WHO) (1946). Constitution of the World Health Organization. Basic Documents, Geneva: World Health Organization.

If you are citing a specific article or paragraph of a constitution, the format of the reference is:

Title of document art. xx, para. x.

Begin the title with the abbreviated name of the body and use the abbreviation 'Const.' for 'Constitution'. 'art. xx' stands for 'article number'. If there is no article number, leave this out. 'para. x' stands for 'paragraph number'. Count paragraphs from the beginning of the article. If you are citing the entire article, leave this out. No date or URL is included.

The format for a parenthetical in-text citation is the same as for the reference.

For a narrative citation in the text, include the title of the document, the article number, and the paragraph number, and spell out all abbreviations.

Therefore, a reference and parenthetical citation to the 7th paragraph of the introductory section of the WHO Constitution would be:

WHO Const., para. 7.

The introductory section does not have an article number, so that element is skipped. A narrative citation in the text would be "paragraph 7 of the World Health Organization Constitution" or something similar.