Lohan checked into Betty Ford May 2 as part of a 90-day sentence for reckless driving. Lohan pleaded no contest to the charges in March and agreed to enter rehab, spend 18 months in psychotherapy and serve 30 days of community service.
Doctors at the facility deemed unnecessary the actress' prescription for Adderall -- a drug used to control attention deficit hyperactivity disorder.
TMZ said Lohan feels she needs the drug and has researched other facilities she thinks will allow her to keep taking it.
However, law-enforcement sources told the celebrity news website prosecutors will not approve her move to another treatment center.
"She had 45 days to find a suitable place. She didn't listen to her people and just did what she wanted, so it's her problem now," an insider told TMZ. "Not gonna happen."