The phrase "a longstanding rule of" is correct and usable in written English.
It can be used to refer to a rule or principle that has been in place for a significant amount of time.
Example: "There is a longstanding rule of etiquette that dictates how one should behave at formal events."
Alternatives: "an established principle of" or "a traditional guideline of".
Fortunately, he did have a longstanding rule of never investing in airlines, which were particularly savaged in yesterday's trading.
In June, Southwest Airlines began enforcing a longstanding rule of charging extra-large passengers for two seats.
Though this is a longstanding rule of thumb in animal cognition research, sometimes referred to as the "principle of conservatism," it is not a principle commonly used in human cognition research.
Truth: A longstanding rule of home ownership is that you need to save up a 20percentt down payment before taking on a mortgage.
Both in this case and in the arson case, Jones v. United States, No. 99-5739, the court applied a longstanding rule that laws of dubious constitutionality should be interpreted, if possible, in a way that avoids the constitutional issue.
The Federal Communications Commission is preparing to relax a longstanding rule that limits the ability of companies to own both a newspaper and a television or radio station in the same local market.
In December 2011, The New York Times reported that the Federal Communications Commission was "preparing to relax a longstanding rule that limits the ability of companies to own both a newspaper and a television or radio station in the same local market".
"It's a longstanding rule related to the fact that we have a minimal number of stanchions for displays," Ms. Rosenau said.
For 19-hour flights to return, America's Federal Aviation Administration would probably have to do away with a longstanding rule that requires two-engine planes to stay within a certain distance of runways where they can land in case of trouble.
IN professional kitchens there is a longstanding rule: there can be only one head chef.
"This is a longstanding rule, not just for these Games but all Games.
