"falls within rules" is a correct and usable phrase in written English.
You can use it when referring to a situation which adheres, or is contained within, a certain set of rules or regulations. For example, "The decision of the court falls within the rules of the legal system."
A defender may also block, check, or hit the player with his body, as long as his action falls within the rules defining allowable contact.
Cuba's refusal in the two high-profile cases falls within the rules governing the I.O.C., whose charter states that an athlete who switches nationalities must wait three years to compete for the new country.
In terms of intrusiveness, child benefit falls within the benefit rules (the clue's in the name), not the tax rules.
Everyone else within the chain or in support roles falls within the usual rules.
Or rather, given that London is in fact a city, and therefore about the play of individual and collective, whether it falls within the hazy rules of the game.
As it appears that the decision of the court of appeals was rested, in addition to other grounds, upon a distinct and independent ground, not involving any federal question, and sufficient in itself to maintain the judgment, the writ of error falls within the wellsettled rule on that subject, and cannot be maintained.
So keen was the Cabinet Office to help that it changed its normal eligibility criteria to ensure that it fell within the rules.
All samples fell within normal detection limits.
Calcium levels while also significantly different, still fall within normal range, although the possibility of other causes such as malabsorption or decreased dietary calcium intake in some subjects cannot be ruled out.
This case doesn't fall within those rules".
