Lots of people really missing the point here! Palmer sprinted over from one side of the pitch to the other-he got carried away (like we all would have understandably) and it’s alot different from bench personnel/subs etc celebrating on the same side of the pitch,ie by running down the line to celebrate with the team(on the same side of the pitch).
Referee isn’t a fan like most of us with our Sky Blue tinted glasses on and must apply this sanction-it’s mandatory……..
A player who leaves the field of play to correct or change equipment must:
• have the equipment checked by a match official before being allowed to re-enter
• only re-enter with the referee’s permission (which may be given during play)
A player who enters without permission must be cautioned, and if play is stopped to issue the caution, an indirect free kick is awarded from the position of the ball when play was stopped, unless there was interference, in which case a direct free kick (or penalty kick) is awarded from the position of the interference.