Sometimes, if a person has only a rudimentary understanding of an ethical system or of the consequences of their actions, it is possible for “ethics” to be used as a justification for self-indulgent behaviour.

I’m operating here from a consequentalist perspective. Non-consequentialist systems of ethics may lead to a different conclusion.

Two examples:

  1. It is sometimes the case that “breaking” a vegan diet reduces suffering. These tend to be corner cases and don’t justify eating meat and animal products in every day situation. But e.g. if you’re at a restaurant, you order a vegan burger, and you instead receive a burger that has cheese on it, it might cause more suffering to order a second burger; this is because no food causes zero suffering, so wasting a cheese-containing burger and increasing your demand by ordering an extra burger has an ethical cost.
  2. Some ethicists have argued that athletes in competitive team sports have an obligation to their teammates to do their best to win. As such, engaging in “dishonest” behaviour, such as cheating, intimidating opponents, manipulating the referee, time-wasting, and so on, might be morally required. In some cases, refusing to cheat can be seen as self-indulgent, as the athlete is placing their own desire (to feel good about their actions) above their obligation to their teammates (to do their best to win the game). Note that this is very different to community sports, where there is less of a moral obligation to win and more of a moral obligation to play fair.

In both of these cases, there is an incomplete analysis of all morally relevant consequences, and this insufficient analysis causes the person to make a (possibly) wrong decision.

This is different from moral licensing (where a person uses a moral choice in one setting to justify an immoral choice in another setting).