The phrase "a strict rule of" is correct and usable in written English.
It can be used when referring to a specific guideline or regulation that must be followed without exception.
Example: "There is a strict rule of conduct that all employees must adhere to in the workplace."
Alternatives: "a firm guideline of" or "a rigid principle of".
It's always been a strict rule of mine that I'd never employ an Australian as my assistant.
As the air wing commander, in charge of all 70 warplanes aboard this carrier, he alone could decide whether to heed a strict rule of anonymity set by the ship's commanding officer, for security reasons.
The 24 Gilbertines, handpicked for their exceptional voices, observe a strict rule of silence among themselves but pray together as a choir, singing the ancient Gregorian chants they believe to be "the word of God sung in the voice of God".
But the researchers said they applied a strict rule of "absolutely no passcode". There was a note of caution from the researchers too, inviting further questions: "Here, I want to repeat that our experiment is a kind of proof of concept, the purpose of which is to prove a principle, other issues will be researched later". The researchers do have history in breaking biometric systems, however.
And as a strict rule of thumb, never, ever, under any circumstances darken your face for a costume.
So when I have serious writing to do, I go to a library near my apartment which has a study room with a strict rule of silence.
Last month the secretary-general of NATO, Jaap de Hoop Scheffer, underlined the need for greater political transparency and a stricter rule of law if Georgia wants to progress towards membership.
I have a relatively strict rule of No Monday Deadlines because they imply weekend work.
A more commonly applied, less strict, rule of thumb is that both the Infit and the Outfit MNSQ are allowed to be somewhere between the 0.7 and 1.3.
What surprised me was not that a strict, rule-based model of education successfully trained students.
The Federal Communications Commission has been working on a draft of a stricter rule defining consent.
