I was interested in this myself and had looked it up through...

I was interested in this myself and had looked it up through comments made by Baker McKenzie. They're lawyers so, needless to say, you then have to take the comments to your own lawyer, if you have one, to understand what the first lawyer said.
There's three considerations (of course, there's never one).
A company is within the law to vary a dividend decision / announcement. It doesn't seem to matter whether the variation represents a deferment or a cancellation as long as it occurs before the payment date. It seems that it's not until the payment date that debt is formally incurred hence the contract to pay the dividend is not formalised until then. Any change to a dividend decision that involved cancellation or deferment after the payment date is reached would, if followed through, be a matter for the courts.
They're the rules if the company doesn't have a constitution. If the company has a constitution, there may be a relevant component of the constitution that precludes the company from making any changes to their dividend announcements. Such constitutional rules would override Company law.
The third consideration is around any change to the SP that occurs around the ex-entitlement date, a date which may then prove to mean nothing. The only recourse there is through the ASX who's sympathies rest with the companies for the time being.