“Medieval church portals and their importance in the history of law” by Barbara Deimling.
a. Secular and church legal business (laws) took place at the portal.
b. Some German church doors were red, and would be considered the place of judgment.
c. Oaths were sworn at the portals.
d. They were a place for an asylum.
e. They had signing of contracts.
f. They did possibly because in the Old Testament it mentions that the elders “dispensed justice” at the gate (cf. Amos 5.15).
Source: Romanesque book on page 327