Former San Francisco Archbishop William Levada, 79, was stopped after a 2015 Nissan Altima was seen swerving in and out of traffic.
He was arrested on 20 August and freed bail.
He's since released a statement apologising for his 'error in judgement' and said he would continue to work with the police during the investigation.
Before his retirement as Archbishop in 2012, he was the highest ranking American cardinal within the Vatican and two years ago he travelled to the heart of Rome to take part in the conclave that elected Pope Francis.
He was first ordained in the Los Angeles Archdiocese in 1961 and was made a Cardinal in 2006.
Spokesman Michael Brown, from the diocese said: "Speaking generally at all levels of the organisation, such things would be looked at on a case-by-case basis.
"Where a lapse in judgment occurred, the matter would probably be considered less serious.
"If the matter seemed to indicate a more serious problem, this would be treated more seriously. This would be true at all employee levels."
Mr Levada is due back in court on the island in September.
