Thus, it was for freedom (legitimate moral and ceremonial freedom)
that Christ set us free.
It seems the author quoted was paraphrasing Galatians 5:1 of the New Testament:
It is for freedom that Christ has set us free. Stand firm, then, and
do not let yourselves to be burdened again by a yoke of slavery.
In the larger context, the author refined his meaning with a specific reference:
the moral and ceremonial liabilities of the Law of Moses.
He also referred to Acts 15, which discusses an ancient theological dispute about circumcision, the fundamental ceremony of Judaism:
Certain people came down from Judea to Antioch and were teaching the
believers: “Unless you are circumcised, according to the custom taught
by Moses, you cannot be saved.” [extensive discussion omitted]... Now
then, why do you try to test God by putting on the necks of Gentiles a
yoke that neither we nor our ancestors have been able to bear?
Emphasis mine
This discussion seems to be consistent with the larger context of Galatians 5:1
Mark my words! I, Paul, tell you that if you let yourselves be
circumcised, Christ will be of no value to you at all.
Emphasis mine
The nature of this ceremonial freedom is a question of theology rather than language, but it seems quite clear that the author of Old Covenant, New Covenant refers to a New Testament notion of freedom from the ceremonial requirement of circumcision, which is at the center of Old Testament Judaism.
Conclusion:
The author's definition appears to be:
- relating to or used for formal events of a religious or public nature.