The dramatic build up to this weekend’s AFLW grand final escalated further on the eve of the game with Western Bulldogs captain Katie Brennan announcing she will lodge a formal sex discrimination complaint against the AFL with the Australian Human Rights Commission. It’s a savvy legal move that will compel the AFL to completely rethink its approach to sanctioning women.

Brennan’s two-game ban raised immediate allegations of sex-based discrimination. The reason was simple: were Brennan were a man, she would have been asked to pay a fine, instead of being suspended. The sole reason women do not get the option of paying a fine is wage disparity (the average wage for a men’s AFL player is $371,000, whereas AFLW rookies receive just $10,500). Rather than opting to have the women pay smaller fines on a pro rata basis, the AFL went with a different system that results in them being sanctioned more severely.

There has been an explosion of public interest in the case this week. There have also been many misconceptions about the relationship between elite sporting competitions and the law. Although sporting competitions are entitled to develop their own rules, those rules must comply with overarching legal obligations. In Australia this includes the Federal Sex Discrimination Act, which prevents discrimination against people on the basis of their sex, except in very specific circumstances.

Brennan twice appealed the suspension. Surprisingly, her legal team didn’t pursue this line of argument at the first hearing. At the second hearing, she did, represented by a team of lawyers including Jack Rush QC and Bulldogs president, Peter Gordon. The AFL argued that Brennan’s legal team should have raised those arguments the first time around, were barred from raising entirely new arguments the second time around, and were simply trying to have a second bite at the cherry. Disappointingly, the appeals board deliberated for just 15 minutes, gave no reasons for its decision, and dismissed the appeal. The failure to provide an explanation for its decision raised even more legal questions, including the possibility that this was itself a denial of a fundamental legal principle – that of procedural fairness.

All eyes were on the Bulldogs’ next move. Gordon is a renowned litigator who rarely shies away from a fight and as social media exploded with speculation, a #FreeKatieBrennan movement was launched, including a petition. There was growing recognition that Brennan was a victim of circumstance, and an imperfect system which yielded a result only made possible because there are different – and more severe – rules for women.

On Friday morning, the Dogs announced that they would not seek an injunction in the supreme or federal court. But then came the kicker. In an unexpected move, the club announced that Brennan is lodging a complaint with the Australian Human Rights Commission, alleging that the suspension was unlawful on human rights grounds.

The Commission will not deal with the case before the grand final this weekend. Brennan will not play. But the lodging of a human rights complaint is a strategic masterstroke that forces the AFL into an impossible position. Here’s why: the Commission is an independent third party, whose job is to investigate human rights complaints and to help parties resolve their disputes. The Commission will ask the AFL to consider the specifics of Brennan’s complaint, before overseeing a conciliation. There, Brennan will sit down with the AFL to air her concerns and the Commission will try to help them both come to a resolution.

Brennan will almost certainly demand three things from the AFL: that they admit the tribunal system unfairly discriminates against women; that they overhaul the system so that the rules are fair and no other woman will be put in Brennan’s position again; and finally, that her suspension be wiped from the historic record, as a matter of principle.

If the AFL does not accede, Brennan can go to the federal court and seek a hearing. The AFL will be taking a huge risk if it allows things to go that far. It cannot afford a formal court hearing where such arguments are thrashed out by teams of lawyers, with QCs getting paid hourly rates comparable to an entire season’s wage for many of the women.

It would be a public relations disaster for the AFL, and generate significant bad blood with players and fans, including the new audience it has found through the AFLW. Most of all, the AFL cannot afford to risk the chance of a formal federal court finding that its fledgling AFLW competition – a pillar of its putative commitment to gender equality and equal opportunity for women – is inherently discriminatory. It would be a disastrous result for CEO Gil McLachlan, and one that he will be desperate to avoid.

For this reason, it’s almost certain that the AFL will capitulate at the first hurdle, and accede to some – and perhaps all – of Brennan’s demands at conciliation. The AFL will be asked to admit that its system – while well-intentioned – wasn’t perfect and produced a perverse result that has left Brennan on the wrong side of history. Her move is a hugely significant one, not just for current AFLW footballers, but for future generations of girls and women who will play the game. A star on the field, Brennan has now laid down a huge challenge to the code off it. The ball is now in the AFL’s court.