ICAO
Not sure if this question was directed to me or to the starter but here's my answer:
If you want a to add a type rating to a US (FAA) licence you need to clear TSA. Including fingerprints, background checks, DOJ letter...you get the point.
ICAO at large doesn't say anything about background checks, but that doesn't mean a specific country, NZ for exemple, won't require some background checks. Each country is different.
Cheers!