On Wednesday the full bench of the High Court will hear a case which will decide whether tens of thousands of Australians get to vote or not on August 21. The advocacy group GetUp! is challenging the constitutional validity of changes the Howard government made to the Electoral Act in 2006. Before 2006, voters had seven days after an election was called to enrol to vote. When the new laws came in the rolls shut on the day the election writs were issued.

GetUp! is arguing that these changes have eroded the voting rights of over 100,000 Australians. And if you look at enrolment figures, they do have a point. During the 2004 campaign 157,311 people enrolled to vote after the election was called. In this year's campaign that figure declined to 85,996 with voters only having one working day to enrol after the election was announced. These numbers don't count those who've tried to change their enrolment details in the same period.

So why did the Coalition government change the laws in the first place? John Howard said at the time it was about "maintaining the integrity of the roll" and that there was "plenty of evidence" of rorting of the rolls.

In 2007, I asked Gary Nairn, the minister responsible for the electoral laws if he could give me some evidence of vote rigging in the close of rolls period. He couldn't provide any, saying, "But there's no evidence that there hasn't been as well".

But before these laws were introduced the Australian Electoral Commission (AEC) had done plenty of research. Following allegations of voter fraud, the AEC scrutinised all the federal elections between 1990 and 2000. In a period in which around 60 million votes were cast across four elections and one referendum, they found only 71 cases of electoral fraud. Most of these cases were considered to be mistakes or too frivolous to lead to prosecution.

If there was any evidence of vote rigging in the close of rolls period, the AEC didn't find it. Instead they found "There were no cases that disclosed any organised conspiracy against the Electoral Roll for federal electoral purposes".

So why change the laws? At the time, critics suggested it was a cynical attempt by the Coalition to reduce the amount of young people on the roll. The conventional wisdom is that first time voters are more likely to vote Labor. At a speech to the Sydney Institute in 2005, Senator Eric Abetz dismissed these claims.

Quoting a study of the 2004 election by Professor Clive Bean, Senator Abetz said that 41 per cent of under 25s gave their primary vote to the Coalition and only 32 per cent voted Labor. These figures were accurate, but Senator Abetz neglected to mention that 17 per cent also voted Green, with the majority of their preferences flowing back to Labor. In a Roy Morgan poll of 18-24s conducted last week Labor was polling 62.5 per cent in two-party preferred terms.

In June, Labor tried to reform the electoral laws. A bill designed to change the close of rolls period back to seven days passed through the House of Representatives. But it never made it through the Senate. The bill had the support of the Greens and Independent Senator Nick Xenophon, but was opposed by the Coalition. The bill's passage was in the hands of Senator Steve Fielding. Senator Fielding gave no undertaking which way he would vote, and Labor failed to introduce it to the Senate.

The failure to pass this bill has meant that people like Shannen Rowe aren't able to vote at this election. Shannen is an 18-year-old student from South Australia. She is one of the plaintiffs in GetUp!'s High Court challenge.

Shannen filled out an enrolment form on Monday July 19 and was planning to drive to her local AEC office before the rolls shut. But like many students, she was short on cash and petrol, and didn't have enough in the tank to get her to the nearest AEC. Shannen Rowe didn't lodge her enrolment form till later in the week.

Shannen and others like her should have enrolled to vote earlier. But not every 18-year-old is great with deadlines, and not all of them are the kind of political nerds who enrol to vote the minute they turn eighteen.

If our independent electoral commission can't find any evidence of vote rorting in the old seven-day close of rolls period, surely we should go back to that system. We should be doing all we can to encourage young people to participate in our democratic system, not finding ways to rub out their votes.