We have treaties addressing issues like these, and generally it is an accepted principle of international law that a country can regulate a company that chooses to business with its citizens.
But Google would not be doing business with Australian citizens. It would be serving them webpages, but it would not take nor give them any money. That said, I'm skeptical that such treaties exist. Would you like to point a specific instance of such a treaty out?
"Serving them webpages" is a business activity under international law. The consideration is the ads they show alongside search results.
As for resources on such treaties, visit the OECD website and you'll be inundated with the model treaties that form the basis of the actual treaties between countries. (Some treaties involve many parties, most are between two nations.) Since you're not paying me, I will simply point out that under America's tax treaty with Australia, the Technical Explanation would note that providing services to another country's citizens is an activity covered by the treaty, and Australia's tax office has plenty of documentation saying the same.