Sportal.co.nz 24.Jun.2013Getty Images
Horwill was cited after appearing to make contact with Welsh lock Alun Wyn Jones' face in the fourth minute of Australia's 23-21 loss to the Lions in the first Test in Brisbane on Saturday.
Wyn Jones required stitches around his eye after the Test, leading to the tourists making a formal complaint against Horwill.
The 28-year-old's case was heard in Melbourne – where the second Test will be played on Saturday – and he was found not guilty after lengthy deliberation.
Judicial officer Nigel Hampton QC ruled that he could not be certain that Horwill had intentionally stamped on his opponent.
"After hearing all the evidence I could not find that when James Horwill's right foot came into glancing contact with Alun Wyn Jones' face, he was acting recklessly," Hampton said.
"I found that I could not reject as being implausible or improbable Horwill's explanation that as he was driving forward with his right leg raised, he was spun off balance through the impact of Lions players entering the ruck from the opposite side.
"In an endeavour to regain his balance, Horwill brought his right leg to the ground unknowing that Alun Wyn Jones' head was in that area, due to having his sight impeded by the presence of Michael Hooper and Tom Croft, who were beneath him and over the top of Alun Wyn Jones.
"Due to these reasons I cannot uphold the citing."
Horwill was naturally relieved to have received clearance to compete in the second Test and is eager to switch focus to on-the-field matters.
"It's never nice hearing things like that (the accusation)," he said.
"I'm very happy with the process and how it went and I'm very happy with the result.
"We hit the ground running tomorrow (Monday) and focus on doing everything we can to win a series-tying Test against the Lions here in Melbourne on Saturday. That's where all my focus is on now."
The news will come as a boost to the Wallabies, who already have the likes of Pat McCabe, Digby Ioane, Adam Ashley-Cooper, and Berrick Barnes in doubt for the must-win clash at Etihad Stadium.