Yes, but his language teaching skills come from his CELTA and DELTA, not his degree in History.

My point is that simply having a degree in an unrelated subject does not qualify you to teach English. A degree in History did not teach your friend how to explain the use of the past perfect to his students, his C/DELTA did. So his degree in History has no relevance to his job as an English language teacher. I'm sure he is gainfully employed, the standard for employment is met by his degree and his C/DELTA.

I'm not saying that they can't be employed, just that ideally any teacher should have a relevant degree, a teaching certification and an ESL certification. Also, a DELTA requires a minimum of two years teaching experience before being undertaken, which means the only training your friend had prior to becoming a teacher was at most a 4 week classroom based certification (The CELTA), compared to somebody who had studied English and then sat a PGCE also, whose students do you think are getting the better deal?

Someone with a C/DELTA and no degree and someone with a C/DELTA and a degree in an unrelated subject are equally as unqualified when compared to somebody with a relevant degree and a teaching certification. My point is that if you have sat an ESL certification and have a fake degree, it really is no different to having sat an ESL certification and have an unrelated degree. Attending university does not automatically qualify you to teach English.

The standard for teaching should be related degree, PGCE (or country specific equivalent) and an ESL certification, preferably with the DELTA being sat when possible.