The seven time world champion passed Ferrari's Fernando Alonso at the last corner of Sunday's race, after the safety car that had been deployed for the Jarno Trulli/Karun Chandhok crash pulled into the pits.
There is a new rule in 2010 that allows overtaking between the safety car line and the finish line.
Where the confusion arises is that if a race finishes under the safety car, there is no overtaking allowed even though the safety car itself pulls into the pits.
Ferrari and Mercedes disagreed fundamentally in the stewards' room, and ultimately the officials declared that Schumacher had breached article 40.13 of the sporting regulations.
The rule states that if the race ends under the safety car, "the cars will take the checkered flag as normal without overtaking".
In lieu of a drive-through penalty, 20 seconds has been added to Schumacher's time, meaning he drops from sixth place to twelfth.
But Mercedes' Ross Brawn believes that because the cars raced at full speed to the checkered flag rather than in slow formation behind Webber, all the teams acknowledged that the safety car period had ended.
"I think you saw the reaction of all the other drivers," said the Briton.
"If what Stefano (Domenicali) has said was true, they would just cruise to the start/finish line because they knew they couldn't be overtaken, but everyone went for it and I'm afraid Fernando was a little asleep and we took advantage."