Art. 56 OG; admissibility of federal civil appeal in matters of inheritance tax liability; a dispute is not open to civil appeal where the cantonal courts decide it exclusively under cantonal law and merely invoke Art. 24 ZGB or Art. 3 of the federal act on domicile and residence by analogy. Tax liability is an issue of public law, relating to the individual's subordination to state authority, and thus belongs to cantonal administrative law rather than to civil law (consid. 1).