This is a difficult question to answer because it is opinion-based.

For what it's worth, I would not include it unless:

It is relevant to the position that he is applying for.

OR

Not including it would cause a significant gap in his employment history.

This is a difficult question to answer because it is opinion-based and the reception/reaction to it being on a resume will vary widely.

For what it's worth, I would not include it unless:

It is relevant to the position that he is applying for.

OR

Not including it would cause a significant gap in his employment history.