In a 7-0 decision, the high court says the only way the Crown's decision to seek a mandatory minimum can be reviewed is if there is an abuse of process.
The case involved an aboriginal man charged with impaired driving who was notified the Crown would be seeking a mandatory minimum sentence.
This being his fifth impaired-driving conviction, he would have spent at least 120 days in jail.
His lawyers argued his aboriginal status had to be taken into account before any decision was made that would limit the judge's sentencing options by imposing a harsher penalty.
The Supreme Court overturned the lower courts' decisions and sentenced the man to 120 days in jail.
The case is likely to be relied upon in future cases involving aboriginal offenders and mandatory minimum sentences.
Two cases scheduled to be heard in December will consider whether the Conservative government's changes to mandatory minimum sentences for some gun crimes are constitutional.
They were enacted as part of the Conservative government's 2008 omnibus bill and the Supreme Court cases will be a test of the Tories' tough-on-crime agenda.