Highfields Capital was founded in 1998 by Jonathan Jacobson, the former portfolio manager of Harvard Management Company, which manages the University's endowment.

Harvard invested $500 million in Highfields' founding, Bartley said.

"They basically gave money to their employee, and said, 'You can do your own thing with it,'" Bartley said. "It's not a detached relationship."

In addition to its leading position in Park Place, Highfields also owns large shares of Station Casinos, Lakes Gaming and other gambling companies, according to the most recent Securities and Exchange Commission Findings, Bartley wrote in the PSLM letter.

"Gambling comprises the largest segment of Highfields' equity portfolio when ranked by industry," he wrote.

And, in direct contrast to endowment funds invested directly by Harvard Management, there is no accountability mechanism in place, Bartley said.

Since Highfields is a private company, their investment portfolio is not included in the Annual Report on Shareholder Responsiblity--a summary of investments that discusses Harvard's responsibility with regards to corporations whose securities are owned by Harvard.