Brooke Mueller's Lawyer She's Clean as a Whistle

6/2/2012 6:00 AM PDT

Brooke Mueller's Lawyer: She Didn't Test Dirty for Drugs

Brooke Mueller did NOT go back into rehab because of a drug relapse -- she went back as part of a pre-scheduled maintenance program approved by a judge -- Brooke's lawyer tells TMZ.

Yale Galanter says when his client pled guilty to cocaine possession last month, she told the judge she had made arrangements to go back to rehab 4 times over the next year.  The reason -- Brooke did great in rehab in the past, and then quickly lapsed back into the world of cocaine upon her return to L.A.

Galanter says after consulting experts, a decision was made that she needed to spend a couple of weeks in rehab every few months, which would make it easier for her to continue life in a city like Los Angeles which is filled with temptations.

Galanter tells us Brooke takes several drug tests every week as part of her probation,and she has tested clean every time.  Arnie Mordkin -- the Pitkin County D.A. who prosecuted her -- seems to back Galanter, telling us he has no evidence Brooke has fallen off the wagon.

As for reports Brooke recently got wasted at Charlie Sheen's house, Galanter says it's B.S. -- if she did she would have never passed her drug tests.