who can judge & teach?
those who get permission from their teacher.
Provided they don't know too much, and are blemished.
It is speculated that Rav does not have Rebbe's permission to rule on blemishes found in 1stborn animals, as he is too much of an expert and would permit things that others would forbid. and the untrained eye would not be able to discern the difference, and thus standards would fall... alternatively there could be better teachers out there, teaching accurately so that the community is not kept in ignorance.
Many, many connections to be made about who is a judge, who teaches torah and who decides halacha today...