>How would this data be held and who would see it or have access to it?
Same way as its currently held - by the various governments with (limited) agreements in place to to check each other's databases. Its not that big a leap to have a unified system in place I think. Or at least starting with the 1st world countries.
Not a fan of big government, but this is an area where I think streamlining things would help.
>European countries already issue biometric passports that require you to provide your fingerprints
Yeah got one of those. The fingerprints aren't actively used at borders though - just facial recognition.
How would this data be held and who would see it or have access to it? The privacy implications would be enormous.
Ironically, many European countries already issue biometric passports that require you to provide your fingerprints before the passport is issued.
But maybe it doesn't really matter - you already provide so much of your personal details when you travel to another country.