In the United States, there is case law[1] establishing that an exact replica of artwork that is itself in public domain is not eligible for copyright protection, because "originality" is a necessary element for copyright protection to exist. Works that lack any originality are therefore public domain even if they require effort or technical skill to produce, such as photographing a public domain painting, or presumably scanning a public domain bust.

Is there any similar law or regulation in Germany?

[1] https://en.wikipedia.org/wiki/Bridgeman_Art_Library_v._Corel....