pen names in MLA works cited pages

The main source for a paper I writing is a unpublished (web only) non-fiction author and not well known who just happens to be a close personal friend who writes under a pen name. Am I required to give his real name in the works cited or somewhere else or can I just use his pen name. Please note that with some research it is trivial to link the two names and the actual work is copyrighted under the pen name. Both me and him have the following concerns:

* If the copyright and all the citations are to a "unknown" pen name does citing the pen name only (and the copyright message to) make it harder to prove authorship

* Several times in the past when I used his real name in web forums where he uses his pen name exclusivally he has sent me private email saying that he highly disapproves but in the case of this paper has no problem with his real name being used *IF AND ONLY IF* MLA and/or the law requires it (the ironic part of this is a he just took the Bar Exam but for criminal and not intellectual law so has very little idea about this)

Good morning.

In this case, you should use the pen name. When citing, you should use exactly what was listed in the publication as the author. Also, if it is his/her wishes that the pen name be used, I am not aware of any law that requires you to go against those wishes.
The whole purpose of citing is so that your readers can locate any information in your text which they would like to know more about. If they are searching for this author, you want to provide them with the name that is listed in his/her publications.

I hope this helps.

Regards,
Gloria
Moderator, EssayForum.com