Kernrechtsfrage
Whether the complaint against the cantonal court's joinder decision was admissible under Art. 87 OG
Extrahierter Entscheid
The joinder decision was a final decision for the appellant and had to be challenged immediately; the later constitutional complaint was therefore inadmissible.
Extrahierte Begründung
The court held that the decision definitively determined the appellant's procedural position, and because later participation could no longer influence the final merits decision, Art. 87 OG required immediate challenge.