HP broken which law exactly?
I don't think that HP has broken US trade sanctions. The export and re-export of pretty much everything from US to Iran is restricted, but as HP did not export anything to Iran the re-export by Redington is where blame lies.
One of the previous posters seems to be suggesting you need an end user certificate for IT equipment and, unless it was classed as a munition, you don't. The US person selling a printer is under no obligation to determine where the product will end up ultimately. But being willfully blind - not asking questions when a reasonable suspicion exists that a US export law will be breached by the buyer of the equipment - is against the law.
A friend told me a few months ago on a visit that pirate copies of Vista are freely available in markets in Tehran. Just think of damage they are doing ...