Millions of people want to donate their organs after they die for transplantation, and many of them have registered their wish to do so or told their family and friends about their decision. For most of them, however, this wish is unlikely to be fulfilled, as only a small number of deaths (1% in the United Kingdom) occur in circumstances where the opportunity to donate organs is possible. Even for those who do die in the "right" way and have recorded their wishes or live in a jurisdiction with a "presumed consent" system, donation often does not go ahead because of another issue: their families refuse to allow donation to proceed. In some jurisdictions, the rate of "family overrule" is over 10%. In this article, we provide a systematic ethical analysis of the family overrule of donation of solid organs by deceased patients, and examine arguments both in favor of and against allowing relatives to "veto" the potential donor's intentions. First, we provide a brief review of the different consent systems in various European countries, and the ramifications for family overrule. Next, we describe and discuss the arguments in favor of permitting donation intentions to be overruled, and then the arguments against doing so. The "pro" arguments are: overrule minimises family distress and staff stress; families need to cooperate for donation to take place; families might have evidence regarding refusal; and failure to permit overrules could weaken trust in the donation system. The "con" arguments are: overrule violates the patient's wishes; the family is too distressed and will regret the decision; overruling harms other patients; and regulations prohibit overrule. We conclude with a general discussion and recommendations for dealing with families who wish to overrule donation. Overall, overrule should only rarely be permitted.