Avi K
“If a person comes to us, tells us he is Jewish and keeps mitzvot we believe him unless there is reason to suspect him. See נאמנות אדם על יהדותו by הרב עקיבא כהנא. ”
Sigh. A rather absolute statement.
It depends, for example, on where he is coming from
According to most, Ethiopian or similar self identification was not enough