It was a quick decision from the Union Cycliste International commissaires after vision from the overhead pictures of the sprint clearly showed Sagan forcing van Aert aside with his head to create a path late in the sprint for stage honours.
Sagan first passed Clement Venturini (AG2R La Mondiale) close alongside the barriers before trying the same thing with van Aert. The gap between van Aert and the barriers was too tight however, and Sagan used his head on van Aert to clear some more space.
The move allowed him to pass van Aert and claim second on the line, behind Caleb Ewan (Lotto Soudal) but just ahead of green jersey rival Sam Bennett (Deceuninck-QuickStep).
Sagan was relegated to the last position by the race jury after the finish applying section 2.12.007, 5.1 of the UCI rules and regulations, negating the 30 points he would have received, with a penalty imposed taking away 25 per cent of the points awarded to the stage winner. That was 50 points divided by four for 12.5, rounded up to 13 points penalty. Coincidentally it was exactly the same as the 13 points that Sagan gained at the intermediate sprint point, meaning that the seven-time green jersey winner stayed at the same points tally as pre-stage.
The battle in the green jersey opens up dramatically in Bennett's favour as a result, now stretching out to 68 points with Bennett on 243 points and Sagan on 175.
Sagan's team BORA-hansgrohe didn't appeal the decision, tweeting out afterwards that they accepted the decision.
The Tour de France continues tonight with Stage 12, the longest of this year’s race, a 218-kilometre course similar to an Ardennes classic from Chauvigny to Sarran. Watch the race on the SBS ŠKODA Tour Tracker from 7.40pm AEST, with television coverage starting from 9.30 AEST on SBS HD.