Well. You actually cast some doubts on my knowledge of French procedural law... so since, France is a civil law country I went to the Code de Procédure Pénale. So small class about what happen when a Judge d'Instruction (which in France is an independent judge who is charged of preparing the case to be judged in a formal court. But only on serious crimes affairs, or when it's a complex affair. So it's like an "expert" prosecutor for serious cases which job is not to actually prosecute... but to really gather the evidence for a fair trial (he has the mission of searching evidences for and against the suspect) I will use JI to refer to this judge) want to speak to someone.

3 cases :

1 - The person is not seriously suspected of being the perpetrator of the crime investigated. He can be forced to present itself to the JI if the JI wants it. Then he will be considered a witness. This is Art. 101 of the CPP (Code of Penal Procedure) In the case of an external impossibility (meaning that it's not just the guy not wanting to come) the JI can actually go to the witness or hear the witness by any mean (Art. 109 CPP). So even if you are a just a witness you can be forced to come.

2 - An assisted witness Art.113-1 CPP (that's when there is some possibility that you are going to be indicted because you are a suspect), the difference is that an assisted witness has the right to have a lawyer, more rights etc.
If you have been identified at least by name by the victim, then you must at least be this. So at least. Assange would have been an assisted witness. It's true that an assisted witness has the right to ask is own indictment, and the JI must comply (Art. 113-6 CPP). BUT, to have the assisted witness status you must have been heard at least once by the JI. Force can still be used to present to assisted witness to the JI, and in case of impossibility etc. etc.

3 - Indicted (Mise en examen). A lot of rights, but also much much much more power to the JI investigating the case. And well, the indictment defined at the 80-1 and 80-2 CPP is quite clearly possible after a face to face interview between the JI and the suspect : Translation by myself "The indictment can only happen after the first interview of the person in front of the JI"...

I could go on explaining the fine details of this law... but I think you got the picture.

Oh, and about your "string of cases"... I'm really sorry to say it... but you totally misinterpreting them. I mean... radically.

See Walser v. France => The problem was that the plaintiff in this case was arrested to be presented to a JI, she (the plaintiff) was then held in custody of the police for more than the legal 48h (58:30 actually) and the only had her first meeting with the JI and was then indicted, benefiting of all rights and protections of the indicted (a lawyer, access to the role of events and her own file etc.). The ECHR says it right away, the problem was the lack of due diligence by the police, not the arrest in itself. The European Judges said that the maximum time to be detained before a presentation to a prosecutor is 48h outside of extraordinary situation (Like the case I cited of Medvedyev v. France, where since it was an extraordinary situation (Medvedyev and all where caught in the middle of the ocean 10 days away from the nearest French coast, so they said that since they where presented right away to a judge after landing, it was legal).

So clearly the Good Court of Strasbourg is not objecting the fact that the suspect was forced to surrender to French police to be then questioned by the Judges and Prosecutors. The Wise Court is saying that police waited too long and thus abused authority. And French law was modified accordingly, creating the articles 803-2 803-3 in the CPP saying that the suspect must be presented in the legal time and quicker possible.

Oh... but maybe you're referring something happening at a totally different moment in the procedure. Yeah... you know, the act of surrender as a prisoner... just before a supreme court trial if, and only if he had been judged guilty by the appellate court. Nothing to do with the indictment, the investigation and everything. It's only that French law required that if an appellate court said you were guilty and sentenced you to a prison sentence, then you had to first go beyond bars to be able to require an appeal in front of the supreme court. This element of law has been deleted of French law in 2000, yes. But has nothing at all to do with the present case. And as I show, the Court is perfectly fine with authorizing the police to arrest people so they can be presented to a judge to be indicted and then investigated, which is exactly what is going on here with Assange... This cases are filled in the Access to a Tribunal Rights at the ECHR books, not the rights of persons being investigated.

TL;DR:
Omar and etc. are cases concerning the fact that in France before 2000 if you where sentenced to prison by an appellate court, you had to surrender yourself to the police in order to be able to appeal to the Supreme Court. If you were on the run, your lawyer couldn't file an appeal to the Supreme. But this has nothing to do with the present case. Since Assange already filed complaints in Sweden about decisions by the prosecutors and etc. And the ECHR is perfectly fine with an arrest in investigations, provided it is to present the suspect to a prosecutor or judge (and some other cases also).

Finally : Assange has a fundamental right to file appeal even if he is on the run. But the prosecutors have the right to ask police to bring Assange by force if he denies coming willingly.

----
Now speaking of the other comments you made :
----

On the subject of respect of the rule of law by Sweden and UK, you are right. Nothing impedes UK and Sweden than become worse than China on that matter. BUT, frankly... that kind of thing does not happen out of the blue. Guantanomo and Pvt Manning is out of scope, that's US, and we both agree that Justice in the US is quite needing in everything that concerns """"National Security"""". We are speaking of Sweden and UK here.

Oh and... about the special relationship... sooo if this relationship is so special... and since, I pretty sure Sweden's relationship with US is not at allll that special, why the hell would he be afraid of going to Sweden to be extradicted to the US ?