A Charles Sturt University political science academic is not surprised by the High Court ruling that Deputy Prime Minister Barnaby Joyce and four Senators were invalidly elected to Parliament at last year's federal election.

The five parliamentarians held dual citizenship with New Zealand, Canada and Great Britain respectively and the Constitution is explicit in disqualifying such people from the Australian Parliament.

Associate Professor of political science in the CSU School of Humanities and Social Sciences Dominic O'Sullivan is concerned that it is bad for democracy that the public debate on this issue has followed only the line that the Members of Parliament should have known the rules and should have followed them.

"There is a bigger issue at stake," Professor O'Sullivan said, "That is, whether the national interest is well served by excluding from Parliament those Australian citizens who may for important cultural and family reasons wish to retain a formal association with their countries of origin.

"Others like Mr Joyce, whose father was born in Dunedin in 1924 and migrated to Australia in 1947 - before Australian or New Zealand citizenship was created, one was simply a British subject - have retained no connection to the 'foreign power' that some argue compromises one's ability to serve Australian interests alone."

Professor O'Sullivan noted that almost half the Australian population was born, or has a parent born, overseas.

"When this figure is coupled with those ineligible for election to Parliament because they hold an 'office for profit under the Crown', one sees that the Australian Parliament cannot easily be fully representative of the Australian people," he said.

"The High Court has previously held that a school teacher could not be elected to Parliament by virtue of being on the public payroll. There is a legal challenge underway against David Gillespie's eligibility to sit in Parliament. His alleged 'office for profit' is that he lets a small commercial property to Australia Post."

Professor O'Sullivan argues that last week's High Court decision is an opportunity to consider which of their fellow citizens Australians want to be allowed to be elected to Parliament and which they do not.

"It is important that people understand that this issue is primarily about them and who they want to be allowed to support in an election," Professor O'Sullivan said.

"We diminish our authority as voters if we reduce this issue to cynical revenge against the political class," Professor O'Sullivan said.

Professor O'Sullivan wonders whether Australians' general cynical disdain for Members of Parliament is because so many are, themselves, ineligible to be elected.

"A more broadly representative Parliament could help democracy to work better," Professor O'Sullivan concluded.