"McKinnon sits IN THE UK, and commits a crime by accessing computers in the US. Ergo, he is committing a crime IN THE UK"

Section 4 of the Computer Misuse Act, says that the English courts have jurisdiction in any hacking ("unauthorised entry" - regardless of intent) cases where "at least one significant link with domestic jurisdiction must exist in the circumstances of the case for the offence to be committed."

In other words, had McKinnon sat in the US (or Maldives or anywhere else on or off the planet) and hacked a UK system, the English courts would be able to prosecute him - regardless of whether the country he was in considered his actions a crime.

OK so getting him here would pose different problems, but if we are happy to declare things committed in other countries to be crimes, we have to accept some reciprocity.