According to TMZ.com, the child custody agreement between the former "Two and a Half Men" star, 45, and his most recent ex-wife, 33, does not require either of them to undergo drug testing.
Sheen famously lost his sitcom job after a January bender and told ABC News' "20/20" that he was "banging seven-gram rocks" of drugs while partying. Mueller has been to rehab multiple times.
A representative for Sheen declined to comment on TMZ's report. Representatives Mueller did not immediately respond to ABCNews.com's requests for comment.
The former couple's divorce became official on May 2. Since then, they've gone to court multiple times to hammer out details of their custody agreement regarding their 2-year-old twin sons, Bob and Max.
Mueller currently maintains primary custody of the boys.
The parents' history of drug abuse has come up often in the legal proceedings. In court papers filed before the March custody agreement, Mueller said she was struggling with her sobriety and attending a day program as well as living with a sober companion. She said her mother would assist her in caring for the children, according to the documents.
The documents also said that for a time in January before custody became an issue, Mueller and the twin boys lived with Sheen and his two then-girlfriends, Natalie Kenly and Rachel Oberlin.
Mueller, Sheen and the two girlfriends even went on vacation to the Bahamas together, but Mueller alleged that Sheen was drinking and his behavior turned violent. She said that Sheen punched her, threatened to stab her with a pen knife and spit on her feet, according to the documents.
Mueller said Sheen also told her that he "hated his ex-wife, Denise Richards, violently and he was going to have her hair shaved off," according to the court records.
Mueller and Sheen married in May 2008. In November 2010, he filed for divorce.