One consequence of the tragedy over MH17, apparently at the hands of Russian-backed separatists, is that it raises the question of whether President Putin should attend the Brisbane G20 Summit in November. Some newspapers are reporting that Australia is threatening to ban Putin.

The predominant view among the Australian public is probably that Putin should not be invited to the Brisbane Summit. But things are not straightforward and Australia may be placed in an invidious position. Moreover, depending on how things develop, the character of the G20 may change significantly.

The G20 is an informal forum. There are no rules on membership or revoking membership. Decisions are based on consensus. As such, it is not really up to Australia to decide not to invite a G20 member to a summit. This was made clear to the Australian Foreign Minister in March. In response to comments from Julie Bishop suggesting that Russia's participation in the Brisbane Summit could be brought into question because of events in Ukraine, the BRICS (Brazil, Russia, India, China, South Africa) foreign ministers issued a communique saying that they 'noted with concern, the recent media statement of the forthcoming G20 Summit to be held in Brisbane in November 2014. The custodianship of the G20 belongs to all member States equally and no one member State can unilaterally determine its nature and character'. The Russian Foreign Minister went further and said 'we altogether not just Australia formed the G20'.

But to repeat, there are no formal rules, and events have moved on since March. There are a number of scenarios as to how things could play out in the lead-up to the Brisbane Summit. The preferred outcome would be for Russia to co-operate on all fronts, including the investigation of the crash of MH17, bringing the perpetrators to justice, and resolving the situation in the Ukraine. In such a situation, tensions over Putin's attendance in Brisbane would decline.

Another scenario is that Russia's belligerent attitude continues and intensifies in coming months. All G20 members are outraged and agree that Russia's actions are such that they should not participate in the G20, including official meetings, the G20 finance minister meetings in September and October, along with the leaders' summit in Brisbane.

Such an outcome would change the character of the G20.

It would move from being purely an economic forum. A precedent would be set and political and security considerations would be a factor in determining future attendance, and would likely be discussed at the summit.

A third scenario is that Russia's attitude is considered less than acceptable to many countries but that some G20 members oppose excluding Putin from the Brisbane summit. The view of the BRICS will be particularly important. So far China has warned Western nations against rushing to implicate Russia. At the BRICS Summit on 16 July, leaders condemned the sanctions imposed on Russia to date. The position of some other European countries may also not be straightforward. Much of Europe's response to imposing sanctions on Russia prior to the crash of MH117 was weak, primarily due to the close economic interactions between Europe and Russia. Europe failed to present a united front on sanctions against Moscow and the Netherlands was among the European countries least inclined to challenge Russia.

If the last scenario develops, Australia could be in an invidious position.

Australian public opinion, and that in some other countries, may remain strongly opposed to allowing Putin to attend the Brisbane Summit. It is possible that, given such controversy and the prospect of a hostile reception in Australia, Putin may choose not to come. But if Australia did not let Putin attend, other countries may oppose and conceivably bring into question their attendance. Should this eventuate, the future of the G20 could come into question, particularly if those not attending were major emerging markets. The strength and significance of the G20 is that it brings together the leading advanced economies and emerging markets. In addition, political and security issues would be brought front and centre in G20 deliberations, overshadowing the economic agenda.

The coming months could be very tricky ones for Australia, given its role as G20 chair for 2014. At this stage the Prime Minister's approach is appropriate. He has been firm in his condemnation of the situation, acknowledged that Russia's attendance at the Brisbane summit is an issue, but said Australia would be reluctant to act unilaterally because it is an important international gathering and that it is necessary to see how things develop.

Photo by Flickr user Bohan_Shen.