Hartley was cited for what many viewed as an accidental clash with prop Rabah Slimani in the 30th minute of last Saturday’s defeat to Clermont Auvergne at Stade Marcel Michelin.
He had been shown a yellow card by referee Ben Whitehouse following the incident and was later cited by match citing commissioner Douglas Hunter.
That meant Hartley faced a hearing in London on Wednesday, but the case wasa dismissed as the committee was not satisfied that the offence had warranted a red card.
And Mallinder issued a strong response after the outcome was announced.
“The decision to cite Dylan from Saturday’s game against Clermont was unjustified,” the Saints boss said.
“This was a run-of-the-mill rugby incident during a high intensity game of European rugby.
“Anyone who watched the game could see that this was completely accidental – a misjudgement at a clear–out, plain and simple.
“When we should be preparing for a crucial league game against Wasps this Saturday, we have instead been distracted by what we believe was an unwarranted judicial hearing.
“Citings like this do beg the question of whether Dylan is being singled out for what has happened in the past rather than being judged solely on Saturday’s game.”