Some fundamental rights may be interfered with "by or on the basis of a law", others may only be restricted "on the basis of a law", and before a constitutional amendment in 1968 there were also fundamental rights that could only be restricted "by a law".
The discussion about whether these differences in wording have competence-related significance in the sense that encroachments on the fundamental rights in question may only be made directly by law without subsequent administrative execution ("by a law") or only by administrative execution ("on the basis of a law") is older than the Basic Law itself.
In his basic contribution to fundamental rights dogmatics, Tobias Mast discusses conceivable interpretations and argues for a norm-specific interpretation of their limits.
Mast, Tobias (2023): Die kompetenzielle Bedeutung der Grundrechtsschranken [The Competent Significance of Fundamental Rights Barriers], In: Archiv des öffentlichen Rechts (AöR) 148 (2023), pp. 154-203.
