Here is the link to Article XIV: https://bookofconcord.org/augsburg-confession/of-ecclesiastical-order/
This article is only one sentence long: “Of Ecclesiastical Order they teach that no one should publicly teach in the Church or administer the Sacraments unless he be regularly called.”
When the Roman theologians responded, they agreed with the article, but insisted that “regularly called” must be understood to mean a canonically valid ordination. In other words: a priest/pastor must be ordained by a Roman Catholic bishop who has valid apostolic succession.
In reply, Melanchthon observed that the Lutheran pastors would have gladly accepted canonical ordination: they had no wish to establish a new church. However, while church polity can be useful, this custom is not strictly necessary because it derives from human authority rather than scripture. The Catholic bishops refused to recognize the truth of the evangelical doctrine; instead of ordaining the Lutheran pastors, they condemned them. Hence, it was no longer possible to maintain the old procedures. (https://bookofconcord.org/defense/of-ecclesiastical-order/)
In later centuries, Article XIV would generate different kinds of controversy. At times, it has been used to keep laypersons from exercising their gifts. Some Lutheran churches interpret this quite strictly and insist that the pastor should even do all the scripture readings in the divine service. In the Lutheran Brethren, we have more of a history of lay involvement and even lay preaching.
I don’t claim to be an expert on this issue, but it appears to me that the article should not be read as an absolute prohibition on lay ministry. It is more of a recognition that there should be good order in the church, and that those who serve in a public teaching role should do so under authority. (This is Biblical: some relevant New Testament passages include Acts 14:23; Ephesians 4:11-12; James 3:1-4; 1 Timothy 3; Titus 1:5-9; 1 Peter 5:1-4.)
However, if someone is particularly gifted in ministry, it seems to me that the congregation should affirm their gift and consider issuing them a “regular call” (a relevant case study might be Acts 18:18-28, where Priscilla and Aquila came alongside an itinerant evangelist and equipped him). Furthermore, while the pastor and elders are ultimately responsible for what is taught, it seems that in the New Testament, other people were sometimes given the opportunity to share during gatherings, within proper guidelines (see 1 Corinthians 14).
Additionally, we affirm the priesthood of all believers (see especially 1 Peter 2:5-9). Outside of the public worship service, every Christian has a responsibility to speak the word of God as they go about their ordinary vocation.
As for the sacraments:
- For the sake of good order, baptism should normally be administered by the pastor. However, in an emergency (such as impending death), if there is no pastor available, any Christian can (and should) baptize.
- In some other protestant traditions, it is fairly common for laypersons to baptize. Though we do not prefer this, so long as the baptism was performed with water and the words “I baptize you in the name of the Father, and of the Son, and of the Holy Spirit,” we would recognize that it was valid. It’s the word of God that makes it so — not whether the baptizer was ordained or not. [There are some exceptions to this. For example, the Mormon church uses the correct words, but they have a false understanding of the Trinity and therefore mean something different by the words. Hence, Mormon baptism is invalid. Mormons are not Christian.]
- For the sake of good order, holy communion should normally be administered by the pastor. In the Lutheran Brethren, elders are also ordained and have authority to administer communion. It’s not that a layperson can’t, but it would be presumptuous to do so without a calling.
- In situations where there is no ordained pastor (for example, in a place where there are only a few Christians), my personal opinion is that the congregation has authority to delegate someone to read the words of institution. This would still be a “regular call.”