tary oversight under Art. 44(1) first sentence GG and the right to collect evidence pursuant to Art. 44(2) first sentence GG (cf. BVerfGE 67, 100 <128 and 129, 132>; 124,
78 <116>). In the investigation of political matters, files are of paramount importance
as means of evidence. […]
2. The right of a parliamentary committee of inquiry to collect evidence is subject to
limitations; any such limitation, including those set out by ordinary statutory law, must
be rooted in constitutional law (cf. BVerfGE 124, 78 <118>).
111
a) Accordingly, obligations arising under international law cannot immediately limit
the parliamentary right to collect evidence, given that these obligations do not have
constitutional rank. In particular, this becomes apparent in the constitutional provisions of Art. 25 GG and Art. 59(2) GG.
112
Art. 25 first sentence GG provides that the general rules of international law shall be
an integral part of federal law. This provision renders the general rules of international
law directly effective (i.e. without requiring any further legal act of ordinary law) within
the German legal order. Pursuant to Art. 25 second sentence GG, the general rules of
international law take precedence over the [ordinary] laws. A law that conflicts with a
general rule of international law therefore violates the constitutional order within the
meaning of Art. 2(1) GG. At the same time, however, Art. 25 GG must be construed –
in accordance with the wording of its second sentence – as conferring upon the general rules of international law a rank above (ordinary) statutes but below the Constitution (‘in-between’ rank, Zwischenrang) (cf. BVerfGE 141, 1 <17 para 39 et seq.> with
further reference).
113
According to Art. 59(2) first sentence GG, international treaties that regulate the political relations of the Federation or relate to subjects of federal legislation become effective within the domestic legal order only by way of the act of approval required under this provision. Art. 59(2) first sentence GG does not merely determine the
methodological approach to the way which provisions of international treaties become effective within the legal order; it also determines the rank within the legal order
conferred upon international treaty law that is given legal effect in such manner. It follows from Art. 59(2) first sentence GG that international treaties share the rank of ordinary (federal) statutes under domestic law, unless they fall within the scope of application of a more specific opening clause (Öffnungsklausel) – especially Arts. 23 to
25 GG; therefore, international law treaty does not general enjoy a rank above statutory law, let alone the rank of constitutional law (BVerfGE 141, 1 <18 paras. 43 et
seq.>).
114
The principle of the Constitution’s openness to international law (Völkerrechtsfreundlichkeit) does not supersede the varied provisions of the Basic Law governing the
rank of the different sources of international law, nor can it set aside the systematic
approach set out in these provisions (cf. BVerfGE 141, 1 <26 et seq. para. 65 et
seq.> and <30 et seq. paras. 73 et seq.>).
115
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