The situation is very different.
|Greenland: Beautiful, just not relevant to the Brexit discussion.|
Greenland exited in 1985 and retained OCT status (Overseas Country and Territory) due to its political links with Denmark, therefore the citizens of Greenland actually remained EU citizens.
It was also considered feasible due to the small amount of people living in Greenland. Free movement rights were kept by other EU nationals living in Greenland (obviously not necessary to do it the other way around).
We also see The Telegraph has jumped on the Vienna Convention acquired rights argument, however, the President of the CBI has stated that this still needs to be clarified by the European Parliament. He also states that of course this will not apply to UK citizens who want to move to the EU or to UK citizens who want to move within the EU following a Brexit.
The situation will not be the same following Brexit, and we really wish the Brexiters would stop saying that it is.