Hi Sergii. Rarher phrase it this way: "The rule should be carved in stone" or "There should be a rule that is carved in stone"

The procedure is not carved in stone. (We can change it). My decision is yet not carved in stone. (I might change it). This expression is often used with 'not'. My reply is certainly not carved in stone. I may change it later :-)

The rule should be carved in stone. These rules should be written in stone.