In england-and-wales, an illuminating judgement of the Court of Appeal explores the relationship between such terms as "bound to fail", "not arguable", "no rational basis", "unfounded", "misconcieved", "hopeless", "totally without merit", and "no realistic prospect of success"; Wasif v Secretary of State for the Home Department  EWCA Civ 82. This arose in the context of a judicial review application, where procedural rules allow some claims to be rejected at an early stage, rather than proceeding to a full hearing.
The normal course is that the claimant (the person who objects to a decision the government has made) will file papers with the court describing their claim. If the judge deems their case "arguable", then it can carry on, ultimately with the judge deciding who is right. If not, then there can be a "renewal hearing", where the applicant can explain their case orally, in the hope of persuading the judge that their case is arguable after all. But if the judge says the case, on the basis of the written material, is "totally without merit", then there is no renewal hearing, and we are done. The claimant could file a fresh case, if the judge's reasons for denial gave them enough clues about what might be arguable instead, or can appeal the finding. Evidently, then, some points can be not arguable, but also not totally without merit.
In Wasif, the court differentiated between (paras 15ff):
- Cases where the judge "can see no rational basis on which the claim could succeed" are certainly bound to fail, and a hearing would be pointless; they are totally without merit.
- Cases which contain a rational argument, but the judge "is confident that, even taking the case at its highest, it is wrong". Notwithstanding the judge's confidence, it is possible that his mind could be changed if an oral hearing took place, so these should not be deemed to be totally without merit. They are described as "not arguable" at this stage, but the claimant gets to argue that they are arguable.
The decision is one involving, well, judgement, and is not totally precise, but the experienced judges in Wasif felt that it was a realistic distinction in practice.
The court points out (17(3) and (5)) that a hearing gives the claimant the chance to address specific issues the judge has noted, especially when they are self-represented and their documents are not well-prepared. In those instances, the judge might be able to spot an actual arguable claim lurking in the material, and "the correct course" could be to refuse permission but allow an oral hearing so that the real issue can be drawn out.
What we can see from this is that a point might be "not arguable" (the judge thinks it is plainly wrong), but still have some level of merit at that stage (the judge is willing to let the claimant address his objections). When the judge comes to deliver his opinion at the very end, he might still say that a particular point is without merit (he has heard all about it and thinks it is completely wrong) even if he'd conceded earlier that the claimant deserved a chance to present it.
Not all arguments that fail are described as "without merit". If Bob prevails in Bob v Rob it does not follow that all of Rob's points were hopeless. Judges can deploy colourful opprobrium but are just as likely to recognize that some arguments are strong, even when the opposing argument was stronger. Equally, a judge might decide that neither Bob nor Rob is completely correct, and the real answer is some other position - even when they both presented reasonable arguments that were worth hearing.