Yes you're right @medici, the trading policy listing rule...

Yes you're right @medici, the trading policy listing rule relates to people rather than the company.

I've done a bit more digging, ASIC has a regulatory guide ( https://asic.gov.au/media/lemm2rcl/rg110-published-5-july-2007-20210603.pdf ) which summarises the Corporations Act "for companies, their advisors and investors involved in or affected by share buy-backs"

Of note is RG 110.37 "A listed company must also make appropriate ongoing disclosure to the market to: (b) assure the market it is not buying back shares while possessing inside information in breach of the insider trading provisions"

So it is a law, but of course inside information will not explain every pause in a share buy-back, there could be any number of reasons.

Some other interesting aspects of buy-backs:

• The company must disclose: "the reasons for the buy-back (as a matter of best practice, this should include a short description of why other ways of returning excess capital have not been chosen)" I think this is often the most interesting disclosure and the statement I go to first when a buy-back is announced. Companies rarely state that they are buying back shares with surplus capital 'because the shares represent good value to the shareholder' but really that's the only reason we want them to do so.
• RG 110.31 If a company has not commenced buying back shares under a notice of a buy-back after two months, we will regard the notice as having expired.

Most of the other aspects to the guide are familiar to most who've participated in share buy-backs. Dry topic I know, but there might be another nerd out there!