public KafkaPrincipal kafkaPrincipal() {
        int colonIndex = principal.indexOf(":");
        if (colonIndex == -1) {
            throw new IllegalStateException("Could not parse principal from `" + principal + "` " +
                "(no colon is present separating the principal type from the principal name)");
        }
        String principalType = principal.substring(0, colonIndex);
        String principalName = principal.substring(colonIndex + 1);
        return new KafkaPrincipal(principalType, principalName);
    }
A Kafka ACLs which is identified by a UUID and stored in the metadata log.
metadata/src/main/java/org/apache/kafka/metadata/authorizer/StandardAcl.java