A very interesting article on the subject was published here:
Babak Shakouri Hassanabadi, "Legal implications of an encounter with extraterrestrial intelligence," in The Space Review, 15 June 2015, http://www.thespacereview.com/article/2770/1
Michael Salla wrote a commentary on the article, which can be found here:
Michael Salla, "Extraterrestrial contact: international law and crimes against humanity," in The Examiner, 20 June 2015, http://www.examiner.com/article/extr...ainst-humanity
UPDATE: On 27 June, one week after the article was published, Michael Salla's article was removed from The Examiner, and he was removed as an author. A copy can, however, still be found at: http://exopolitics.org/extraterrestrial-contact-international-law-crimes-against-humanity/