Ann Biezanek, 65, a locum doctor and homeopath from Wallasey, Merseyside, was found not guilty at Liverpool Crown Court of five charges of possession and supply of cannabis bought for her daughter.
The jury had heard details of a 'serious and intractable' illness which had afflicted Lucy, 33, for 13 years. Dr Biezanek admitted supplying the drug, but claimed the illness, made partially manageable by cannabis, placed her as a mother and doctor under great duress.
She provided the drug because of the extraordinary circumstances, a defence of necessity which the jury of seven women and five men took 50 minutes to accept.
Tony Ostrin, her solicitor, said: 'The Government should look now at the 1971 Misuse of Drugs Act and amend it to enable doctors to supply cannabis to any patient they thought needed it.
'Before 1971, her actions would not have been illegal. This case shows that cannabis can be supplied, providing it can be shown to have been necessary and if someone is forced into a similar position to Dr Biezanek's.
'I don't think a prosecution like this will happen again. Someone who wasn't a doctor would not have the necessary medical expertise - the defence of necessity is more readily available to a doctor.'
Dr Biezanek, a widow and mother of seven children, listened impassively as the verdicts were announced. She refused to comment, but Mr Ostrin said she intended to resume part-time practice.
'She feels great relief. She has been under terrific strain, although she believes she did the right thing in the circumstances. She is a decent, honorable, respectable person who dealt in the best way she could with a tragic situation.'
Cannabis alleviated Lucy's symptoms, the court was told. Dr Biezanek had bought the drug in small quantities, some of which was intercepted when mailed to Lucy in Inverness.
Dr Biezanek said she took responsibility for obtaining the supply because her daughter was on bail and could not risk buying it herself. Her condition improved; she began to put on weight and sleep better.
'I felt very pleased that I had been successful in getting some (cannabis),' Dr Biezanek told the jury. 'I became a criminal because my conscience said it would be wrong of me to continue to obstruct her.'