An Australian Federal court decision in 1999, for example, required an Australian branch of a Maltese bank to produce documents held in Malta for use in Australian criminal proceedings.

The Patriot Act may make it "slightly easier" for the US government to access data, he says, but it does not change any fundamental principle.

Nor are the provisions of US legislation regarding access to data unique to data held by US companies. "Like all US laws, the Patriot Act and related laws apply equally to every company doing business in the US, whether or not the company is based in the US."

Moreover, given that most countries cooperate closely in law enforcement matters, it is likely that even if none of the data is in the US, the US government -- or the Australian or New Zealand government in similar circumstances -- could gain access to it by using bilateral mutual assistance treaties on law enforcement, he says.