AI Overview: "In conclusion, the idea of supplied jurisdiction extending to cover an antipope's creation of cardinals is a contradiction of canonical principles. It would require the Church to validate an act that, by its very nature, is a public rejection of the Church's own legitimate authority"

AI Overview

There is no Catholic Church theory that states supplied jurisdiction makes cardinals appointed by an antipope valid

. An antipope has no legitimate papal authority or jurisdiction to appoint cardinals, so any such appointment is canonically null and void. 

Here is an overview of the concepts in your query:

Supplied jurisdiction

• In Catholic Canon Law, supplied jurisdiction allows the Church to provide governing authority in extraordinary, exceptional circumstances for the good of the faithful.
• It typically applies to cases like confession or marriage where a priest lacks normal faculties but the faithful are in danger of death, or when there is common error or positive and probable doubt about a priest's faculties.
• The Church itself, the Mystical Body of Christ, is understood to supply the jurisdiction, not an earthly superior. 

Antipopes and their appointments

• An antipope is a person who makes a false claim to be pope in opposition to a legitimately elected one.
• Because an antipope lacks true papal authority, all of their official ecclesiastical acts, including the appointment of new cardinals, are invalid.
• Cardinals created by an antipope are called "pseudocardinals" or "quasi-cardinals".
• Historically, during periods like the Great Western Schism, rival claimants to the papacy created their own colleges of cardinals. When a single pope was eventually recognized, the appointments made by the antipopes were annulled. 

Why supplied jurisdiction does not apply to antipopes

The theory of supplied jurisdiction cannot be used to validate an antipope's appointments for several key reasons:

1. Scope of application: Supplied jurisdiction is invoked for specific, limited acts for the spiritual good of the faithful (e.g., confession, marriage). It does not grant general legislative or governing power, which is what is required to create a cardinal.
2. No error in the faithful: Supplied jurisdiction is sometimes applied in cases of "common error," where the faithful reasonably but mistakenly believe a priest has faculties. No such error could exist regarding a claimant to the papacy, as the legitimate successor is a matter of public fact, and the validity of a papal appointment is not based on the perception of the faithful.
3. Source of authority: The Church supplies jurisdiction from its own divine authority, in place of a priest's ordinary human superior. An antipope, by definition, is acting against the Church's authority, making it impossible for the Church to validate his illegitimate acts. 

In conclusion, the idea of supplied jurisdiction extending to cover an antipope's creation of cardinals is a contradiction of canonical principles. It would require the Church to validate an act that, by its very nature, is a public rejection of the Church's own legitimate authority.