> I wonder what would happen if the US gave these assurances then broke them ?
The English courts are permitted to take into account whether assurances for previous extraditions have been complied with:
> When considering the adequacy of an assurance in any particular case, the courts should place appropriate weight on any assurance previously obtained in extradition requests from the same requesting country.
...this is of little comfort to Assange, but it does mean that there is an incentive for the country issuing the assurances to comply with them, otherwise their future extradition requests have a greatly increased chance of being denied.
The English courts are permitted to take into account whether assurances for previous extraditions have been complied with:
> When considering the adequacy of an assurance in any particular case, the courts should place appropriate weight on any assurance previously obtained in extradition requests from the same requesting country.
http://data.parliament.uk/DepositedPapers/Files/DEP2016-0191...
...this is of little comfort to Assange, but it does mean that there is an incentive for the country issuing the assurances to comply with them, otherwise their future extradition requests have a greatly increased chance of being denied.