I've looked into it before and I didn't find anything suggesting that it's a law. It appears to be willful collaboration with the feds and other nation states, possibly to avoid the attention of regulators, but it's all done in secret so there's not a ton of info.

Along similar lines, scanners and commercial software packages like Photoshop attempt to detect EURion dots and the digital watermarking that replaced it in currency. Obviously open source software has no such thing because it would be pointless, and it's not illegal that it doesn't.

For whatever reason, these antifeatures seem to also be missing from commercial digital cameras.

> Is this a federal (US) mandate or a law in any other country?

No, its a backdoor regulation in the US (probably using the threat of actual regulation premised on controlling counterfeiting to get firms onboard) via agreements from manufacturers to act without regulation.

The legislations for the 35 member countries of the CBCDG can be viewed here:

https://rulesforuse.org/en/about-cbcdg

e.g. for the US dollar:

https://rulesforuse.org/en/currencies/us-dollar

Information on the CDS developed by the CBCDG is sparse:

https://en.wikipedia.org/wiki/Central_Bank_Counterfeit_Deter...

It is in the US