Dressed in his race kit but covered with a grey jacket, Froome (Team Sky) was accosted on his descent back down the final climb to his team accommodation.
Froome came off his bike and fell to the ground before getting up, looking to be very angry with the policeman in question.
Froome was descending along with his Team Sky bodyguard when the incident happened but there haven't been any further repercussions yet.
Riders who have finished the race often descend down the final climb of a stage, even when the race is still on. This is especially prevalent when there is no space at the top of the mountain for team buses and support vehicles.
However, amateurs and members of the public aren't allowed to ride on the race route while the road is closed under race conditions and police are there to make sure members of the public walk their bikes alongside the race route rather than ride them.
It completes a poor day for Froome, with the four-time Tour de France winner losing time on the mountainous Stage 17 to his rivals in the final few kilometres of the race.
In a separate clash, Froome's teammate and current leader of the Tour, Geraint Thomas, was grabbed at by a spectator as he descended the final. Thomas managed to stay upright and there was no indication that there were further issues after the initial altercation.
Team Sky haven't made a statement about either incident at this point.
Stage 17 of the Tour de France for 2018, and it was an experimental stage, won by Quintana, and a stage that may have had an impact on Chris Froome, as G is moving into the Sky leader seat.