A “typical” rights cumulative clause:
Somewhere, once upon a time, one of our learned friends must have had a near-death experience, psychotic episode, or somehow hit on the paranoid thought that a cause of action conferred by contract might inadvertently squish an analogous one arising at common law or under a statute.
Well, it might, but only where the theory of the game suggests it should — and there, you shouldn’t need a “rights cumulative” clause and, if you have one, it won’t work anyway.
Where it will work, the proposition that “unrelated rights are cumulative where they don’t overlap” goes without saying, so — well, you don’t need it there, either.
Where “rights cumulative” will work, it isn’t needed
I might pass you my manuscript under a confidentiality agreement: your publication of it in breach of that agreement may entitle me contractual damages, but my direct losses as a result — the traditional measure of contractual damages, of course — might add up to a lot less than your resulting profits — which the common law might regarded as unreasonably speculative losses beyond the reach of an aggrieved contracting party — as a result.
No matter: because I hold the copyright in the manuscript, I can exercise my statutory right to have you account to me for those profits too — but where my contractual damages and your profits coincide, I can only recover once. There is an arid intellectual discussion to be had about which prevails in a time of conflict. Nothing hinges on it, but it seems to the JC that one’s proprietary statutory rights under a copyright pre-exist any rights you might have under this or that contract, so a claim for lost profits through breach of copyright always comes first. This means the contractual damages under a confidentiality agreement in and of itself are likely to be meagre. This is a perennial problem with confidentiality agreements, and is the reason for all that mush about equitable remedies and injunctions.
Where was I? There is no suggestion that a fellow waives her copyright by signing a contract (unless the contract clearly says that), so she should hardly need a rights cumulative clause to satisfy herself that her rights are cumulative, unless she deliberately waived them, where they won’t be.
Where “rights cumulative” won’t work, and isn’t wanted
Sometimes, rights arising in different magisteria of the law aren’t cumulative. That is inevitable, you should embrace it, and a hastily injected “rights cumulative” clause is a chocolate teapot anyway.
There is generally no concurrent liability, for example, in contract and tort, because they are the yin and yang of civil liabilities: tort is the system of rights and obligations that are presumed to exist between otherwise unconnected souls whose existences happen to interfere with each other, but who haven’t directly agreed what the rights and obligations between them should be — “neighbours”, in Lord Atkin’s well-oiled phrase, but not “lovers” (in mine).
Tort is the business of describing the elusive point at which strangers become neighbours, and articulating a practical public morality between them of the sort that hateful fellow on the Clapham Omnibus might contrive. Those presumptive, “when all else fails” rules fall away when neighbours become intimate enough to agree specific bilateral rules of engagement between them. Then they are contracting counterparties, and those specific rights and duties they have worked out for themselves — their contractual obligations — override the general principles that tort would otherwise apply. It is true that a tortious relationship will pre exist a contractual one — it is hard to get close enough to someone else to engage in intimate contractual relations with them without becoming neighbours first — but seeing as the very point of a contract is to dispell all those uncertainties, it seems to me contractual obligations are, at their essence, intended to dispel tortious ones.
So if I have, in full possession of my senses, agreed to do something unreasonable or stupid, and you, in yours, have agreed to pay for it, I cannot appeal to rules derived from misadventures with gifted ginger beer, escaping wild animals and mis-hit cricket balls to excuse my commitment.
Now construction lawyers will jump up and down and say “but what about Henderson v Merrett?” and they will have some colour of justification for doing so — see concurrent liability for more — but none of this really impinges on financial contracts, and quietly I’m not sure there is genuine concurrence, even there.