The phrase "definitive rules" is correct and can be used in written English.
You can use it when describing a set of specific and absolute guidelines or regulations that must be followed. Example: The company has established definitive rules for employee conduct, including dress code and attendance expectations.
Norms had since begun to emerge, but no one could point to any definitive rules.
Gaiman, in an article for, shares what he believes to be the definitive rules for writing.
The broadband proposal is now open for a period of public comment, after which the F.C.C. will craft definitive rules to be voted on by the five commissioners.
I am often asked whether a statement should be written in the first or third person and, while there are no definitive rules about this, my preference is always to write in the first person because the CV is all about you and your skillset.
"You can't write definitive rules yet".
This can be distinguished from 'methodological incommensurability', according to which there is no common measure between successive scientific theories, in the sense that theory comparison is sometimes a matter of weighing historically developing values, not following fixed, definitive rules (Sankey and Hoyningen-Huene 2001, vii-xv).
Two days before she died Pope Innocent IV approved her definitive rule.
I exhausted whatever sources of information I could in search of a definitive rule that said donors should be knocked out of contention at, say, 65.
Although it provided standards for judging sexual harassment claims, the Supreme Court stopped short of creating "a definitive rule on employer liability".
Despite the high effect of appropriately selecting the computer programs' allowable functions there is no definitive rule on choosing them.
Among the puzzling MLP modeling processes is determining the hidden layers' neuron number because there is no definitive rule for that.
