I found this on a USGov site, is it possible your friend holds dual citizenship? I'll try and find if something like this was going on last year, these are for the current year.
Temporary immigration restrictions
Temporary immigration measures come into force on 16 March 2017 for citizens of Libya, Iran, Somalia, Sudan, Syria and Yemen for a period of 90 days. British passport holders (regardless of country of birth or whether they hold another passport/nationality) aren’t affected by these measures.
You’ll generally qualify to enter the USA using the VWP if your British passport:
and you:
- haven’t been arrested for certain crimes, even if a criminal conviction didn’t result
- aren’t a dual national of Iran, Iraq, Libya, Somalia, Sudan, Syria or Yemen.
- haven’t travelled to Libya, Iran, Iraq, Somalia, Sudan, Syria or Yemen since March 2011
- have received authorisation from the Electronic System for Travel Authorisation at least 72 hours before you travel (see below)
- can show that you have enough funds available on arrival to support yourself during your stay, even if you’re staying with family and friends
https://www.gov.uk/foreign-travel-advice/usa/entry-requirements