Japan Exchange Group has revised its guidelines on derivatives trading, following a series of bond futures manipulation scandals at Nomura Holdings and other major global banks.

The amendment seeks to clarify the criteria for reviewing derivatives transactions so that financial firms can establish more effective oversight, themselves, of trading in products, including Japanese government bond futures.

Japan’s largest bourse operator conveyed the revision to market participants at its derivatives exchange in Osaka on Thursday, according to a spokesperson.

Authorities have been working to stamp out misconduct after concluding last year that Nomura engaged in “spoofing” in 2021 in violation of the law. The practice involves placing fake orders to create a false impression of market supply and demand in order to profit from ensuing price movements. JPX and the Japan Securities Dealers Association have been discussing countermeasures at the government’s request.

Japan Exchange Regulation, the independent self-regulatory body of JPX, is revising the guidelines for Osaka Exchange member firms, the spokesperson said. The entity also plans to share information with them on best practices through seminars and other steps to help the companies strengthen internal controls. It will continue to provide the members with advice for improvements as needed.

Traders would benefit from clearer guidance. The line between spoofing and regular transactions can be contentious — a former Nomura trader who is accused of having committed the act four years ago has insisted he is innocent. Some Japanese government bond traders have noted the rules were opaque enough that almost anyone could be tripped up and lose their job.

The revision is the first since JPX created the guidelines in 2020 for companies to review their own derivatives trades, after the Financial Services Agency penalized Citigroup and Mitsubishi UFJ Financial Group in the preceding two years for spoofing JGB futures. JPX shares the guidelines only with member firms, keeping them from the general public.