Art. 29, 30, 31 Abs. 2 OG; direct action before the Federal Court in disputes within its ordinary appellate jurisdiction. Where the Federal Court is designated by law as appellate instance, the parties may not prorogue it as sole instance by agreement. Art. 31 Abs. 2 OG applies only to disputes not otherwise assigned by law to the Federal Court. The rules on the instances are mandatory public law and cannot be waived by private agreement; at most, the intermediate cantonal appellate instance may be omitted, where the statute so permits.