As we learned in Doctor Strange, earth is protected by a magical defense shield known as the Sanctum.
In Avengers: Infinity War once,
Wong was done helping Banner in New York, he said that he had to return to guard the New York Sanctum.
So we can assume that it was still operational.
However, Thanos (and his henchmen the Black Order) seem to travel to and from earth, seemingly with relative ease. What's the deal?
Can the Black Order travel to and from earth, without being affected by the Sanctum's protections?