You can find that in the German "Frequenzverordnung FreqV" (Frequency Regulation).
The frequencies from 430 to 440 MHz are assigned to ham radio and non-navigational location finding use, code number D150.
Under D150 you find the following statement:
"Die Frequenzbereiche 9 – 10 kHz, 13 553 – 13 567 kHz, 26 957 – 27 283 kHz, 40,66 – 40,70 MHz, 433,05 – 434,79 MHz, 2 400 – 2 500 MHz, 5 725 – 5 875 MHz und 24 – 24,25 GHz sind für ISM-Anwendungen bestimmt. Funkdienste, die innerhalb dieser Frequenzbereiche wahrgenommen werden, müssen Störungen, die durch diese Anwendungen verursacht werden, hinnehmen."
Translation:
"The frequency ranges 9–10 kHz, 13,553–13,567 kHz, 26,957–27,283 kHz, 40.66–40.70 MHz, 433.05–434.79 MHz, 2,400–2,500 MHz, 5,725–5,875 MHz, and 24–24.25 GHz are designated for ISM applications.
Radio services operating within these frequency ranges must accept any interference caused by these applications."
ISM stands for "Industrial, Scientific and Medical" applications.
The regulation on the European level are: 2019/1345 and 2014/53/EU
AWo