Hollywood's motion picture academy will not revoke the unexpected best actress nomination for "To Leslie" star Andrea Riseborough, the group's chief executive said on Tuesday after a review of an aggressive campaign on her behalf. Riseborough was nominated for best actress for playing an alcoholic single mother in the little-seen film, a shock to awards pundits who had not expected her to be in the mix. The surprise nomination sparked questions about whether a campaign for Riseborough had violated lobbying rules set by the Academy of Motion Picture Arts and Sciences. Several A-list stars posted social media comments touting her performance. On Tuesday, Academy CEO Bill Kramer said the organization "has determined the activity in question does not rise to the level that the film's nomination should be rescinded." "However, we did discover social media and outreach campaigning tactics that caused concern. These tactics are being addressed with the responsible parties directly," Kramer added. The academy limits how studios can reach out to voters, how often and what they can say in any communications as part of their Oscars campaigns. Winners of the Academy Awards will be announced on March 12.