I assume they are referring to the cease-and-desist letters sent to websites that don't publish an "Impressum"[1] (information about the person responsible for the website, including an address and phone number). It's a holdover from print publications, and there's a bit of legal uncertainty as to whether it applies to small private websites, but the threshold for it being required is really low.

Unsurprisingly, this has created an industry of scummy law firms that specialise in finding infringing websites and sending them cease-and-desist letters with a bill for their legal fees attached.

[1] https://en.wikipedia.org/wiki/Impressum