This verse has been interpreted in various ways, ever since the time of the early church. There are two reasons for this: 1) disagreement over whether this verse should be read as a question or as a statement; 2) disagreement over the meaning of the phrase those who have no standing in the church.
If the verse consists of a statement and not a question, it can be read as follows: So if you have such [trivial] cases, appoint those [church members] who have no standing in the church.
If this is the correct reading, then Paul is telling the church to appoint as their judges those church members who are of a lowly position (probably because these church members will have no personal interest in the outcome of the cases).
But if the verse consists of a question, it reads as follows: So if you have such [trivial] cases, why do you appoint as judges those who have no standing in the church?
This interpretation seems to be more plausible. If it is correct, then Paul is using the phrase those who have no standing in the church
to describe unbelievers.
4 So if you have such cases, why do you lay them before those who have no standing in the church?