High treason is criminal disloyalty to one's government. Participating in a war against one's native country, attempting to overthrow its government, spying on its military, its diplomats, or its secret services for a hostile and foreign power, or attempting to kill its head of state are perhaps the best known examples of high treason. High treason requires that the alleged traitor have obligations of loyalty in the state he or she betrayed, such as citizenship, although presence in the state at the time is sufficient.
Now whether you believe Al-Megrahi is guilty or not the fact remains that the Scottish and UK government conspired to have a convicted mass murderer of British nationals released on behalf of a foreign state power.
Now, they may not hang you for this any longer but suffice it to say Brown, Blair, Mandelson and Macaskill should all be put away for a very long time.