UPDATED: The BBC has a very good “Q&A: [on] Julian Assange and Asylum”, which is actually very good on the legal issues. One of the issues considered is whether there are any ways in which Assange could get out of the Ecuadorian embassy without being arrested. For example, could he smuggled out in a car or diplomatid bag. The BBC says:
“Assuming Julian Assange evaded arrest outside the phone number library embassy, he could get into a diplomatic car. These vehicles enjoy protection in international law from ‘search, requisition, attachment and execution’.
of the Met having the power to stop the car – but no power to search it for Julian Assange.
Even if he got away, at some point he would have to get out of it into an aircraft – at which point the risk of arrest would return.”
This seems right to me. The reference is to Art. 22(3) of the VCDR which says that “the means of transport of the mission shall be immune from search, requisition, attachment or execution.” Note that the language here is different from the language used in para. 1 of that Article which deals premises of the mission. Para. 3 does not say that the means of transport are inviolable. The obligation to respect and protected is more limited than the obligation to respect inviolability. It seems to be accepted practice that there are some limited forms of interference with diplomatic cars which are legitimate, e.g. towing away a car that is causing a hazard or illegally parked, not for the purpose of enforcing a penalty but for the purpose of clearing the hazard. That action is not an attachment or execution.