One of the side's players, Luke Arscott, had tactical information about the Sale Sharks' defence revealed to him by his brother Tom, a winger for the Sharks, the night before the two teams faced each other in January. Sale lost 24-23.
Tom Arscott's contract was terminated on January 20 after disciplinary action and Sale triggered an investigation by the Rugby Football Union.
Luatua's move to Bristol in the British summer for next season was announced on Tuesday.
The Rugby Football Union said it found Tom Arscott's behaviour had been "inappropriate" and gave him a written warning.
"The RFU has determined that this information, while at the lower end of the scale of seriousness, falls within the definition of inside information," it said.
The RFU, who interviewed 25 individuals from both clubs, found no evidence of betting or fixing and also no evidence that Bristol had changed their strategy to deal with Sale's positional changes.
RFU disciplinary head Gerard McEvilly said Arscott's sacking by Sale had been taken into account in determining his punishment.
"These issues have arisen because of the inappropriate sharing of information while players were socialising in the same hotel before the match," he said.
Photo: Brothers Luke Arscott (left) of Bath and Sale wing Tom Arscott share a joke after the Aviva Premiership match between Bath Rugby and Sale Sharks in 2015. Luke now plays for Bristol.