- "Royal Ransomware's web site is bragging that they stole employee data from XYZ Corp." might trigger some legal obligation for XYZ Corp...but my bet would be "nope, sorry, there has to be real evidence that that's true".
- If there is decent evidence that RR actually did steal your data (from XYZ Corp), then "What legal obligation...?" depends upon the jurisdiction.
- Whatever the "what obligations?" answer might be, it's a completely separate question to as "what are the consequences, from my PoV, if they failed to do as they were obligated to?". And again dependent on jurisdiction.