In most legal systems, there is a timeout after that a crime can't be punished any more. It is desuetude.
Currently, Julian Assange can't leave the Equadorian Embassy of the U.K., because he will be arrested for bail violation.
His previous charges (extradition to Sweden for sexual crimes) were dropped.
Does some type of desuetude apply in his case? If yes, when will he be free to go?
Desuetude is the wrong concept. Desuetude relates to laws as a whole falling out of use; it doesn’t relate to individual cases. There is no question that the UK actively enforces their bail laws so they are not falling out of use.
There is a statute of limitations that applies to non-major crimes within which the state must initiate prosecution. However, in this case the prosecution for bail violation has been initiated and Mr Assange is “on the run” so this is not relevant.
Neither is the fact that the original charges that led to his arrest has been dropped- he is wanted for escaping lawful custody under English law for which the penalty is pretty stiff. I will also venture an opinion that the case against him is as open and shut as it comes.
TL;DR
When he dies.
The short answer is that there is no specific time limit for Julian Assange to be tried.
In more detail: Julian Assange was granted bail in the extradition proceedings brought against him as the result of a European Arrest Warrant. He breached bail and so would appear to be guilty of the offence of absconding while on bail (see section 6 of the Bail Act 1976. That is the only outstanding offence being discussed (obviously he may be guilty of a great many other things, but we aren't considering those).
The Bail Act has a special mechanism that may be used for issuing a warrant for the arrest those who have absconded (see section 7). Such a warrant was issued against Assange.
Note that no proceedings under section 6 have yet been brought. It would be accurate to say "he is charged with no crime" at present. In the first of the magistrates' court proceedings this year his lawyers argued that since there was no underlying charge or trial in progress, section 7 was the wrong mechanism and the warrant should be discharged. The judge refused that application.
This is relevant because section 6 is unusual. It may be prosecuted either by "laying an information" (the usual way of starting a summary trial in the Magistrates' court) or as a criminal contempt of court. No information has been laid (it would seem) and there is a time limit of 6 months for doing so under section 127 of the Magistrates' Courts Act 1980.
That means, as far as I can see, the only consequences that Julian Assange could suffer would be committal for contempt of court, which is punishable by up to one month's detention (if tried by an inferior court like the Magistrates') or two years (if by a superior court). But there is, as far as I know, no specific time limit for contempt proceedings.
That is not quite the end of the story. If, reading this, you think that in theory there being no time limit for charging serious offences (and in principle holding a trial of any kind of offence, where someone has fled the jurisdiction), it is possible, though difficult, to force the authorities to drop their prosecution on the basis that their actions are an abuse of process.
This is what Julian Assange's lawyers argued in the second of his warrant applications. Their application was again rejected by the judge.
Having said that, what is true now may not continue to be true. The balance of proportionality may change. It is not impossible that he may be able to have the warrant withdrawn in the future, possibly the far future, but there is no mechanistic time limit as there might be in some jurisdictions.
The judgement refusing withdrawal of the warrant provides some useful background as does the second judgment dealing with the public interest.
Seeking asylum for a legitimate reason is different than "obsconding". The British government knew exactly where Julian was and what he was doing at every moment. He was in London in one of their embassies. They could have gone to him, met with him, at any time if they wanted to check his bail status. Here are definitions and synonyms for absconding. Julian Assange did none of these: absconding -
leave hurriedly and secretly, typically to avoid detection of or arrest for an unlawful action such as theft.
"she absconded with the remaining thousand dollars"
synonyms: run away, escape, bolt, flee, make off, take flight, take off, decamp;
make a break for it,take to one's heels, make a quick getaway, beat a hasty retreat, run for it, make a run for it;
disappear, vanish, slip away, split, steal away, sneak away, clear out, duck out;
Julian did not seek asylum to avoid allegations of sexual misconduct. In fact he attempted to meet with Swedish officials to work with them. He sought asylum because of his fear of extradition to the United States where he would face wrongful criminal espionage charges that did not apply to his case. He never gave classified documents to a foreign country or agent. He only reported classified information to media in the public's interest and for public benefit. That is not a crime.
