I don't think that any country specific statutes or EU commercial code apply in this case. It's a simple matter of contractual statutes and if Namco Bandai reserved the right to withhold royalties under certain conditions and CD Projekt signed that contract then there's nothing that CDP could do about that.
We have contractual freedom in the EU -within the limitations of existing law, of course,- but I don't see which law Namco would violate by including a passage allowing them to withhold royalties if certain conditions (like a pending lawsuit) are met. That would seem like business as usual to me.
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Commercial code and pertinent statutes are often quite relevent to these sorts of disputes - contracts often assert rights that go beyond what is spelled out in the law but they do not actually trump law and commercial code. That you can not trump commercial code in a general manner with contracts is pretty well established - in almost every matter except end user license agreements where some courts treat consumers as being lesser entities in this regard.
If they did reserve the right to with-hold payment under explicitly outlined circumstances, pending a hearing, then some courts might accept this I suppose. That would be unusual and would amount to a contract that effectively allowed one party to prejudicial find the other to be in breach enact a sort self-help remedy. That such specific conditions would be included or that both parties would agree to giving one party what ammounts to powers normally reserved by courts seems a bit unlikely. The specific circumstances would have to be detailed in the agreement though, as courts have (in the US and Europe) consistently ruled against the ability for one party to engage in self help even if they claimed such right in the original contract.
If they had agreed to a contract where the removal of DRM or offering of the Xbox license to another company were specifically enumerated as conditions of continued payment then they were idiots for doing so. Even that though is questionable as courts have generally ruled that even claiming such specific unilateral power to declare the other party to be in breach and take punitive measures is not defensible and does not excuse failure to continue to pay.
In general, if you take punitive measures against a content or service provider before a judicial order appproving such action pending a hearing, you are found to also be a bad-faith actor. In such cases both parties can be found in breach and, if you would have otherwise been found to be acting in good faith, this can only damage your chances to receive and scale of a net-favorable judgement.
Normally, continuing to pay but note that it is in pro-test until a court allows otherwise is the best strategy and avoids you incurring damages yourself. In the case of copyrighted and trademarked material, failure to pay while waiting for a court date puts you in jeopardy of statutory fines - these statutes can not be circumvented or nullified by contractual agreement but those agreements are subject to these statutes. This means that some statutes may allow for specific but limited redress to be included in contracts, but if they do not then claiming these rights does not make them exist.