A note by lawyers at Chapman Tripp, in the firm's last week, suggests "the government has tied itself in knots trying to ban computer programs from the patent regime. It has now sought help from the Intellectual Property Office -- but they are struggling to untangle the mess."

Chapman Tripp and other sources suggest excluding software from patents will contravene the TRIPS (Trade Related Aspects of Intellectual Property) agreement. Article 27(1) of TRIPS says World Trade Organisation members must make patents available for inventions "without discrimination as to... the field of technology." If New Zealand is judged to have violated that clause there could be serious trade consequences, Chapman Tripp says.

MED intellectual property analyst Warren Hassett says most countries provide for some restriction on technology patents and the WTO has not called any of them to account for it in light of Article 27. The topic of software patent was not specifically raised in the negotiations that led to TRIPS, he adds. "We are not convinced that exclusion [of software from patent] is necessarily in contravention of the TRIPS agreement."

The New Zealand amendment bill has a one-line exclusion, reading simply "a computer program is not a patentable invention"; but a set of "guidelines" issued by the Intellectual Property Office suggests many inventions partly implemented in software need not "fall solely within the excluded area" and will therefore still be patentable.