On Tuesday evening, the pair became the second Sydney University team to win the title in three years, securing the university's position as the most successful team in the tournament's 37 year history.

It marks the seventh time a Sydney University team has won the championship since it began in 1981, and the eighth year in a row that it has taken part in the grand final.

The debate was hosted this year by the Debating Society of the Netherlands in The Hague from December 27 to January 4.

In the British parliamentary style debate, four teams of two speakers compete with each other, two representing the "Government" side and two the "Opposition" side.

Teams are given 15 minutes to prepare their arguments after receiving their topics.

Ms Johnstone and Mr Leeder opened the debate for the Government side in the grand final, arguing in favour of universal jurisdiction - the idea that any state can prosecute crimes wherever they occur - for crimes against the environment.

The Sydney pair secured their victory by contending that "environment harms are currently going unchecked and that an international mechanism was the only way to secure better outcomes".

Speakers from Yale University and the University of Oxford formed the Opposition teams, and a duo from Bates College closed for the Government.

The pair were one of six University of Sydney teams sent to the 2017 tournament, which drew students from over 250 universities in more than 90 countries.

To date, Australian universities hold the most championship victories, having won 13 of the 37 tournaments.

Monash University has won five times, and the University of New South Wales once.