  The argument from consistency is related to arguments in favour of ‘formal’ justice, i.e., that two cases which are the same (in relevant respects) should be treated in the same way. It would simply be inconsistent to treat them differently. In the case of precedent this argument is said to favour following the earlier case: assuming that one cannot change the earlier decision (because it is too late to appeal, or the party to the case has reasonably relied upon it, etc), the only way to ensure consistency is for later decision-makers to treat the earlier decision as a precedent. The claim of consistency is also sometimes put in terms of ‘equality’: to treat the later case differently to the first would be to fail to treat the parties before the courts equally. This argument is made independently of other concerns such as parties' expectations or community perceptions of the court process or the problem of moral disagreement. Arguments of this kind certainly have weight in some circumstances. If a legal system is morally legitimate and has authority over those subject to it, then it is inconsistent for one person to be treated less or more favourably by the law than another person whose situation is legally indistinguishable. Other things being equal, legal decisions should be consistent across time and/or decision-makers. A later case should only be treated differently to an earlier case when the law itself has been changed (by the legislator or the courts, including cases where the court overrules an earlier decision in reaching a decision on the case before it) So concerns of consistency provide some justification for treating earlier decisions as sources of law, rather than approaching each question anew when it arises again.