Not quite. As legal explained to me -- it's too legally ambiguous for some entities to feel comfortable using because your only fall back on public domain is copyright, which can be overly restrictive, and the usage rights are undefined and enforcement or rights can be applied or modified at will by the copyright holder in the absence of a clear license. And that copyright, even in the public domain, often exists inherently.
That's not an issue for me at my $corporation because they are sane, but apparently that's the argument.
No illegal per se, would be closer to say it's undefined or that it has no value. IIRC Germany doesn't allow you to disclaim your copyright. A CC0 dedication is probably the best option for a portable public domain option.
Not so much illegal as legally undefined/nonsensical, in most of mainland europe "putting something in the public domain" makes no legal sense and aliases to "all rights reserved".
Here in Sweden, it is not illegal - it is more that there is no legal concept of a public domain which makes any license that try to transfer something to the public domain be nonsense and invalid.
