There's what I consider the 'hierarchy of legal arguments' when it comes to patched software distribution: 1. Trademark infringement. Easy to prove even in a c

There's what I consider the 'hierarchy of legal arguments' when it comes to patched software distribution: 1. Trademark infringement. Easy to prove even in a court, often can get an injunction approved with no further effort. 2. Copyright infringement. Requires some effort to convince a judge that, yes, this is your content, code, or art, and that they did indeed copy and redistribute it, which would cost a few hours of legal professionals' time to draft up in layman's terms, and lead to a few dozens of pages in a court filing. Easier for visual stuff (such as images) than, say, decompiled code, especially as with decompiled code you may even 'accidentally' be violating the patched app's authors' copyright. 3. Anti-circumvention. This is a bit more of a stretch, but if someone doesn't want (or can't afford) a defense, it's easy to spin something in this way. For YT, since there's some obfuscation applied (see the YTDL takedown attempt), one could also easily argue this. Similarly, one could also argue the same if, for example, a video game modification 'works with pirated copies'. 4. 'The far stretch', such as 'runtime patches make a derivative work in memory', some antitrust violations ('their free patches are devaluing our paid subscriptions/microtransactions'), and other 'less' gray-area stuff. 5. Outright challenging the legality of specific types of reverse engineering. This one is tough as it may go the wrong way as well, and this could attract the attention of big financial sponsors (e.g. the EFF) to steer this into 'dangerous precedent'. Now, this case is of course just referring to a C&D, but a lot of companies only send/distribute C&D letters once they also have a court filing for e.g. an injunction ready to go in parallel, for example if the C&D is explicitly refused. Even if that's not the case, refusing it may just as well lead to a court case in a few months, based on another 'technicality' somewhere in this hierarchy. (statement of authority: I've dealt with numerous of these cases in the video game industry, some of them being the accused myself, sometimes involving others telling me their experiences and/or asking for advice other than 'get a lawyer')