Generally, when information is shared among officials that help the crew, or an official, realize that there was a foul, one of them will drop their flag to the ground. Usually it's the official that should have had the flag to begin with.
Enforcing something without a flag should never be done, primarily from on optics point of view.
The NFL mechanic of the wing sharing info with the R for a possible grounding call is a perfect example. The R will listen to the wing, and if a foul was committed, the R will take his flag and nonchalantly toss/drop it to the ground.
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Pope Francis
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