The team believe the allowing of only some lapped cars through contravened the procedure described in article 48.12 of F1’s sporting regulations, underpinning its protest.
This article says that “any cars that have been lapped by the leader will be required to pass the cars on the lead lap and the safety car.”
“Once the last lapped car has passed the leader the safety car will return to the pits at the end of the following lap.”
It believes it also has grounds on which to protest due to the fact that Verstappen appeared to move slightly ahead of Hamilton at least once before the restart, as Hamilton backed up the pack in an attempt to get a strong getaway.
Mercedes is protesting on article 48.8 on this matter, which states that unless an exception applies, “no driver may overtake another car on the track, including the safety car, until he passes the [safety car] line for the first time after the safety car has returned to the pits.”
When asked for his reaction to the protests, Verstappen said, “I think it sums up a little bit the season.”