Maximum wage
People at the top tend to receive substantial sums via share options and the associated dividends. As dividends are unearned income, these would be as exempt from a maximum salary law as they are from National Insurance.
Aside from bonuses, some employees might also receive allowances for accommodation, travel, security, communications, etc.
Of course, those very wealthy people who take no salary but have only unearned income and capital gains would be entirely unaffected.
Nice to see the Greens looking after the very rich.