In the United States, the President "shall have Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present concur" (Art II Section 2). In the UK the ratification of treaties is a matter of the Royal Prerogative. The Executive decides whether or not to ratify a treaty, Parliament has no right to decide.In practice, the 'Ponsonby Rule' has been applied. Mr Arthur Ponsonby (Parliamentary Under Secretary of State for Foreign Affairs) announced in 1924 that "It is the intention of His Majesty's Government to lay on the table of both Houses of Parliament every treaty, when signed, for a period of 21 days, after which the treaty will be ratified and published and circulated in the Treaty Series. In the case of important treaties, the Government will, of course, take an opportunity of submitting them to the House for discussion within this period. But, as the Government cannot take upon itself to decide what may be considered important or unimportant, if there is a formal demand for discussion forwarded through the usual channels from the Opposition or any other party, time will be found for the discussion of the Treaty in question." - in other words, for important treaties, or when parliamentarians request it, a treaty may be discussed before it is ratified.
(for more on the Ponsonby Rule:- http://www.fco.gov.uk/Files/kfile/ponsonbyrule,0.pdf)
It is anticipated that today Gordon Brown will announce an important change. Parliament will be given the RIGHT to ratify treaties (and, another import from the USA, will be able to hold confirmation hearings for appointments to senior public positions)
