That often quoted 2 out of 3 rule has no basis in law, and is wrong as often as it is right.
It sounds good, but really is nothing more than a basis for making further enquiry.
For example, an FAA licence holder can legally take a G registered aircraft and fly it worldwide. This is perfectly legal, and exactly what the UK CAA intend, but fails the 2 out of 3 'rule'.
Equally, a JAR licence holder wishing to fly a N registered aircraft in the USA can not do so, even thought it would comply with the 2 out of 3 'rule'. They must get themselves an FAA licence.
It's a dangerous rule to put too much faith in, and I think it's largely ignored for good reason