How would I cite the US Constitution in Harvard style? How would I go about citing the US constitution (specifically the 1st Amendment) using the Harvard style?

I'd like to add it using Mendeley, but just plain text would be fine.

If someone could let me know, that would be fantastic.
Many thanks.
It would probably depend on where you read the constitution document. If for example you used the constitution documents at the archives.gov website from the comment above your citation would look something like below. I've shown it with the bill of rights as that is where the 1st amendment is located.


  Bibliography:
  Bill of rights transcript text (no date) Available at: http://www.archives.gov/exhibits/charters/bill_of_rights_transcript.html (Accessed: 11 February 2016).
  
  In-line Citation:
  (Bill of rights transcript text, no date)


If, for example you have a book that contains the Constitution you would cite the book. The reasoning for this is that someone can then go look at the same source that you did if they wish.

While I haven't seen anything for Harvard style (so it may be best to seek guidance from someone in your department), in both APA and MLA it appears you can just cite the Constitution directly. APA uses the stylation of the legal blue book which would look something like this;


  In text: A person can say what they want in the United States (U.S. Const. amend. I).
  
  Reference list: U.S. Const. amend. I.


In MLA;


  The 7th edition of the MLA handbook has this to say about citing the
  U.S. Constitution:
  
  "In general, do not italicize or enclose in quotation marks the title
  of laws, acts, and similar documents in either the text or the list of
  works cited (Declaration of Independence, Constitution of the United
  States, Taft-Hartley Act). Such titles are usually abbreviated, and
  the works are cited by sections. The years are added if relevant"
  (205).
  
  Because these directives aren’t very specific, you can use the
  following example as a guide for the Works Cited entry:
  
  U.S. Constitution. Art./Amend. XII, Sec. 3.
  
  You need only provide either the article number or the amendment
  number as appropriate.
  
  The complementary parenthetical citation is written as (US Const.
  amend. XII, sec. 3). You might also reference the U.S. Constitution in
  the sentence itself and only provide the amendment and section number
  in the parentheses at the end of the sentence.