I agree with not PC that the correct answer to this question is no. I agree that the rule to not lie is restricted in scope, prohibiting lying to competent adults who are not violating our rights or threatening such a violation.
Interestingly, not PC seems to think I am committed to rejecting this conclusion. He insinuates that Kantian and Divine Command approaches to ethics entail that one can never lie under any circumstances. He writes for example “that moral principles are neither "divine commandments" nor "categorical imperatives" -- they are guides to action applying within a certain framework of conditions;”and latter he is more explict
Unlike the ethics of religionists, Objectivism derives its moral principles not from stone tablets or burning bushes or caliphate commandments -- not on what's needed to live in heaven or paradise in some supernatural realm -- but from from the needs of man's survival and flourishing right here on this earth. The contrast with religious morality could not be greater: for the Objectivist, moral principles are guides to action intended to enhance and sustain one's life. For the religionist however, moral principles are divine commandments that act like a ball and chain -- a dogmatic straitjacket commanding one's obedience, even if when talking to a Gestapo officer it could lead to your own death or that of a loved one. For the Objectivist, the answer to a Gestapo chief is outside the bounds of morality altogether: morality ends when the Gestapo chief's gun begins. But for the religionist, telling the truth is an absolute necessity even if it entails the sacrifice of your life and that of your loved ones.Here PC is just plain wrong. While it is correct that many Catholic moral theologians support an unqualified prohibition on lying PC misunderstands the rationale they propose for this verdict. Catholic teaching on natural law as (expounded by people like Thomas Aquinas) is precisely that the moral law is derived from what conduces to human flourishing. Lying is prohibited because it is believed to be conducive to human flourishing. It is not prohibited because such a rule makes one fit for heaven or because its set down in tablets of stone promulgated by burning bush (apart from slander lying is not mentioned in the ten commandments) nor is it held to be correct because a priest or caliphate says so. Catholic theologians argue for this thesis from Aristotelian understandings of human flourishing. I think they are incorrect, but thats not an excuse for misrepresenting their position.
Similar things can be said about Divine Command Theories (and contrary to PC not all "religionists" are divine command theorists) . Divine command theories (DCT) as propounded by Locke, Berkley, Paley, Suarez etc typically affirm that right and wrong are determined by God’s prescriptive will. However these thinkers go on to stress that God is a rational being who wills the flourishing of human beings and hence what God’s will is rational and God commands what promotes or leads or respects human flourishing in some way.
But to the more substantive point.
A DC theorist is committed to claiming that it is never wrong to lie in any circumstance, only if believes God has commanded this. Such a claim is often attributed to the Hebrew and Christian scriptures, but this is debatable to say the least. The Hebrew scriptures contain several passages where God approves of lying in certain contexts. One obvious example is the case of the Hebrew midwives in the book of Exodus. In the narrative Pharaoh orders that all Hebrew male children are to be killed at birth. The midwives respond by lying to Pharaoh about the births in order to protect them and are commended by God for their actions. There has been a huge amount of discussion of these passages and their application to moral theology on lying within Christian casuistry. So it is surprising people so often attribute naïve absolutism to moral theologians who take scripture seriously.
Nor does a person sympathetic (as I am) to Kantian understandings of morality have to embrace the conclusion that’s its never wrong to lie. According to some Kantian’s (such as Alan Donagan) ethical principles have a logic such that one person cannot appeal to a principle for protection as a shield for breaking that principle or another equally as grave. Self defence is perhaps the clearest paradigm: a person cannot rationally appeal to an absolute right to not be killed if he uses that right as a shield to cover his killing of someone else. Such a position involves a contradiction of the will. And it rejects the universalizability of moral principles; the idea that what rules one lays down for others must, if they are moral principles, also apply to oneself.
I am inclined to think that without something like this condition ethical principles would become incoherent. If one cannot justifiably use force to repel an attacker when the only way the attacker can be repelled is by force then the attacker has a freedom right to attack his victim. But surely if the claim it’s wrong to kill entails anything it entails that people do not have a freedom right to do kill others. Now, if one can use force against a person to protect ourselves and others from their attacks it seems hard to see why we can’t lie or deceive them to do so.
What does this mean in the present context? It means that not PC is correct that the police are not bound by a promise to pay the reward to those who stole the Victoria Crosses. The Police would be acting licitly if they refused to pay. And nothing about being a divine command theorist or Kantian precludes one drawing this conclusion
Let me add a final point in defence of PC’s conclusion. The standard argument against lying in this context takes a rule consquentialist line. It’s contended that accepting a rule that permits the police to renege on paying such rewards has bad consequences. Criminals in future cases may not divulge information necessary to solve crimes and hence peoples property will not be returned. The problem here, as with many appeals to consquentialism, is that there are other consequences of accepting this rule which point the other way. A rule where criminals get paid for returning what they steal makes stealing and ransoming pay and hence encourage stealing, kidnapping, ransoming etc.
Consequently, if one is to appeal to positive consequences in a plausible way one needs to examine the total consequences of accepting the rule. One need’s to examine both how many crimes will be solved by accepting this rule and how much crime will be encouraged if we don’t and it needs to be shown that former good results outweigh the latter. To the best of my knowledge no one has ever done this calculation. Until they have the claim that consequences justify honouring agreements to thieves is unsubstantiated.