As you maybe noticed, the Wikipedia article has no references, and so it is difficult to determine what is actually meant by calling it a "legal collegium"
In the Roman republic, a collegium was a social society with a common reference for its members such as a specific craft. Carpenters or soldiers e.g. It was a common obligation in the Collegium to secure each other a proper burial.
To become a member you would pay an entrance fee, and also a monthly fee. If a slave member became free during his membership, he was to pay an extra amfor of wine, which was also part of the initial fee.
The article mentioning law could refer to two things as i see it:
- The collegium itself had rules on their own, making them a legal construct.
- It refers to the cesarean period in which every collegium had to be approved by the senate and the caesar.
Personally i think the second possibility is most likely.
The Consuls of Rome are a different story. The Consuls were elected by the people, in a peoples assembly. The people in this case, was limited to adult, male, roman citizens. The consuls were the highest members of the roman magistrate and were elected for a one year term. It was possible for the one consul to veto the other. The magistrate is a term for the collective civil servants of the republic.
"Were the decisions of consuls formally adopted as decisions of the collegium?"
The roman system of power was very intricate and indirect. Especially considering the patron-client system which is explained well in this article https://en.wikipedia.org/wiki/Patronage_in_ancient_Rome If the consuls were members of a collegium it is likely that the collegium had some influence.
"Did the consuls participate with their personal wealth in the collegium?"
Money was a large factor in the roman republic in determining ones social status. Together with the magistrate and the peoples assembly, the roman senate was the third branch of power. to be a member of the senate one needed a fortune of no less than 1.000.000 sestertser. I imagine, but have no proof, that money was also a factor in the power relation of the collegium, especially considering the collegiums promise of proper burial, which is usually expensive.
It seems the Wikipedia article has mixed the republic and the cesarean period, which is of course a problem as it stretches centuries and thus different reigns.
source: susanne william rasmussen, Romerne, Politikens forlag 2006
(Danish book, title is "The Romans" very good introduction to the roman society in general.)