In the UK sodium thiopental is a controlled substance, it is licensed for use as a general anaesthetic (and I think it has other medical purposes).
Your quoted passages refer to the so-called 'export ban'. Following campaigning by, among others, Alistair Carmichael MP and Reprieve, the UK Government prohibited export of the drug without authorisation. In applying for an export licence for the drug you must persuade the Government that it is not intended for use in capital punishment.
The campaigners sought to prevent exports of drugs used in lethal injections. Previously the Government had said it would not ban exports of sodium thiopental because it is a medicine with legitimate medical purposes and in any case could be obtained from other countries, e.g. (in the particular case below) Austria, so a ban would make no difference to the USA's supply but it would harm UK business. Nevertheless the Government maintained its opposition to the death penalty in all circumstances.
That decision was challenged by judicial review - the claimants said the Secretary of State for Business, Innovation and Skills had "acted unlawfully in refusing to exercise his powers under the Export Control Act 2002 to make an order prohibiting its export to the United States". If I understand correctly the judicial review failed on two of the three grounds and decision was deferred on the last ground; subsequently the Secretary of State for Business, Innovation and Skills, Vince Cable, changed his mind as it had emerged the export's purpose was solely for use in lethal injections and the Government had after all committed to oppose the death penalty.
The Queen (on the application of Zagorski and Baze) Claimants - v - Secretary of State for Business, Innovation and Skills and Archimedes Pharma UK Ltd EWHC 3110 (Admin) http://www.bailii.org/ew/cases/EWHC/Admin/2010/3110.html