The lawyer's message doesn't appear to be a DMCA takedown notice at all, but rather a cease & desist, which has nothing like the same weight.
The lawyer's messages don't appear to be claiming that David Slater owns the copyright on the monkey's photos. In fact, they appear to be very carefully worded so as not to claim this.
Don't assume that Slater authorized this. Lawyers on retainer do this sort of stuff all the time while make-working billable hours for themselves. One thing I've learned is that you really have to watch what your lawyers are doing or they'll end up charging you $350/hour to publicly embarras you.
If that is the case you have your lawyers on a very sloppy retainer.
Going outside the terms of a retainer is classed as professional misconduct where I'm from. A lawyer should not take any action on your behalf without, at the very least, implicit instructions to do so.
It's not exactly clear, but it doesn't sound like it was sent to their registered DMCA contact, either.
In short, it really looks like someone was rattling sabers and is miffed that the other side didn't quietly fold, because they know they've got a weak hand.
DMCA takedown has pretty much the same weight as a cease & desist. DMCA does not really give you a bigger stick, instead it offers the recipient a carrot -- follow the rules and you won't be held responsible.
In both cases it's just a request and in both cases you'd have to file a lawsuit to force action.
Sorry, no, that's just wrong. IANAL but it's rather clear that responding to DMCA takedowns is what grants you safe harbor protection, and such takedowns are made under penalty of perjury. Unless you are outside the US or you're happy to lose your protected status and get sued for copyright infringement whenever a user uploads copyrighted content, you can't just choose to disobey it because you feel like it.
Yes, that's my point. Respond to a DMCA according to the rules, or you could be sued. Likewise, respond to a C&D or you could be sued. In fact, since the C&D offers no safe harbor, you could be sued even if you do exactly what it asks.
The threat in both cases is the same. If anything the DMCA is weaker.
You're mixing up the weight of the threat (that you could get sued for this) with the weight of the C&D itself, which at best means "I cared enough to pay a lawyer some comparatively small fee to write this for me" and in this case means bunk. You could even pretend you owned the image and that I broke a million laws, if you wanted - it's not legally binding.
Besides, sending a DMCA takedown doesn't bar the sender from suing you if you aren't an online service provider (e.g. you're a blogger using Wordpress.com, rather than Wordpress.com itself) or if you knew you hosted the supposedly infringing material in the first place. Both of these apply in this case.
The lawyer's message doesn't appear to be a DMCA takedown notice at all, but rather a cease & desist, which has nothing like the same weight.
The lawyer's messages don't appear to be claiming that David Slater owns the copyright on the monkey's photos. In fact, they appear to be very carefully worded so as not to claim this.