An internal report by prosecutors says that after a three-year investigation, they didn't have enough evidence to show celebrity news website TMZ paid the accused officers for the photo, and that became an obstacle in charging them.
The Associated Press report obtained a copy of the March 28 report on Thursday after its contents were first reported by the Los Angeles Times.
Officers Blanca Lopez and Rebecca Reyes may still get fired. They are slated to appear before disciplinary panels in August.
Brown, who was Rihanna's boyfriend at the time, was arrested on suspicion of beating the Grammy winner on Feb. 8, 2009, leaving her bloody and bruised.
The "Umbrella" and "Only Girl (In The World)" songstress, whose full name is Robyn Rihanna Fenty, canceled her Grammy performance that year after the incident.
Brown pleaded guilty to attacking Rihanna and was ordered to serve five years on supervised probation and to complete six months of community service including roadside cleanup, graffiti removal and manual labor.
Prosecutors allege the photo was leaked after a stack of photographs of Rihanna's injuries was left lying on a desk at the Wilshire police station and Reyes took a picture of the top photo with her phone.
Prosecutors say Reyes later emailed the image from her LAPD email address to her personal email address.
Reyes and Lopez were roommates at the time, and phone records showed that they made multiple phone calls to Fox Television and TMZ in February.
The photo shocked fans and prompted a national conversation about domestic violence after it spread through the media.
But despite a search of Reyes' and Lopez's bank accounts, a money trail was not discovered tying the leak to them, prosecutors said.
In order to prove the officers broke the law, prosecutors said in the report they "must prove beyond a reasonable doubt that Reyes and Lopez disclosed the image of Robyn F. (Rihanna) to TMZ and obtained money in exchange for this disclosure."
The prosecutors' report noted that other LAPD personnel had access to the photos.
"As such, although both Reyes and Lopez's actions are suspicious, they are insufficient to support a criminal prosecution," the report says.
Rihanna's attorney Donald Etra said Thursday he does not know at this time whether the singer wants to pursue any further legal action.
"Apparently this was an internal decision by the district attorney. A victim's privacy should be protected," Etra said.