Originally Posted by
UKtravelbear
Countries have always had the right to refuse entry to visitors. They don't have any freedom of movement rights until they are admitted to the country/countries
At least with these sort of authorisations you don't even get on the plane before being denied entry rather than it happen at the border and being sent back.
Can't people still be denied entry at the border? AFAIK having an ESTA isn't proof that the USA will necessarily allow one to enter.