There are no restrictions on entering Greenland for foreigners, who are not required to have a VISA to visit Denmark.
If in doubt foreigners should inquire whether they will need a visa for travels to Greenland.
In the affirmative, passengers must make sure to file an application in due time. There are different rules for residents of Schengen-countries and when traveling via Copenhagen passengers may need a visa for Denmark as well.
Note: A permit is required when the travel is to or through Pituffik/Thule Air Base, which is a military base/defence area. For more information on this, please read the chapter regarding Pituffik/Thule Air Base.