There is a zero limit for under-20s.
Lawyer Gerard Rennie told the court yesterday his client was moving his car 150 metres so others could park closer to the venue of a pre-funeral gathering.
McMaster was intending to sleep in his vehicle that night.
''You have before you quite a stellar young man,'' Rennie said.
He told the court his client had been one of two selected for an international leadership conference in Vancouver.
A conviction, he argued, would be severely detrimental to McMaster's aspirations.
Rennie said the teenager had realistic options of pursuing a university exchange in the UK, Australia or the United States.
There was documentation before the court showing the UK could be ruled out for five years with a drink-driving conviction.
McMaster had also approached law firms to assess the effect of a black mark on his record.
Rennie said they confirmed there was a distinct possibility of it counting against the teen, ''particularly when in the larger firms you have people thumbing through literally hundreds of applications''.
Noting the police were neutral to the application for discharge without conviction, Judge Dominic Flatley indicated he was prepared to grant it.
Before that would be finalised, he wanted the defendant to complete 50 hours' community work and at least two sessions with a substance-abuse counsellor.
''This is, in all circumstances, minor offending,'' he said.
''You are of sound character, there's no doubt about that... other people get a chance. I think you should get a chance as well.''
Regardless of whether the discharge was granted, the judge said he would still impose a period of disqualification.
''I'm very confident this young man will never appear in court - other than representing others,'' Rennie said.
McMaster will be back in court in August.
