Last week's guilty verdict has brought no illumination for foreign companies worried that they too could find themselves violating ill-defined Chinese secrecy laws, writes William MacNamara.

Rio Tinto's convicted former employees in China were found to possess commercially “secret” documents related to the country's steel industry. According to people familiar with findings in the closed-door trial, some documents detailed production cutbacks at Chinese steel mills during the global slump. Others, apparently, profiled various mills' production capacity, iron ore requirements and negotiating positions.

Elsewhere, such information could be easy to obtain while conducting market research. It might even be public. But in China the big steelmakers are state-owned and even basic data are technically secret.