Jon Flanagan escaped punishment for his clash with Scott Brown in last month's game against Celtic because it didn't meet the SFA's "brutality" test.
The Rangers defender won his appeal against a retrospective ban over the incident after being cited in the days after the game at Ibrox earlier this month.
The former Liverpool star was booked by referee Kevin Clancy after knocking Hoops skipper Brown to the floor as they jostled at a corner during Rangers' 2-0 derby triumph at Ibrox.
Celtic were left stunned by the governing body's decision and claimed the decision to spare Flanagan was a "huge embarrassment for Scottish football".
Now the SFA have explained in further detail how they came to their final verdict.
They said: "Having viewed the available footage of the incident, provided by both parties, and having considered the submissions from both parties, the Fast Track Tribunal decided that the notice of complaint should be dismissed.
"The referee saw the incident in question, and, notwithstanding that he did not see the actual point of contact, he saw sufficient to assess brutality and decided that the action of the player was reckless.
"The Fast Track Tribunal took the view that the player made contact with the chest/neck area of the opponent, not with his face or head, and that the evidence did not meet the 'exceptional' test in Judicial Panel Protocol 3.3. Accordingly, the Fast Track Tribunal dismissed the complaint."
Flanagan told the panel he was "merely fending off" the Celtic captain as he "stood his ground, following initial contact with the opponent, as they awaited the corner kick".
