The short House of Lords (Expulsion and Suspension) Act 2015 came into force in June 2015.
A person expelled as a result of such a resolution ceases to be a member. Those suspended are not entitled to receive writs of summons to attend the House and are disqualified from sitting or voting in the Lords - see section 1(2) and 1(3).
has to state that, in the opinion of the House of Lords, the conduct giving rise to the resolution - (a) occurred after the coming into force of this Act, or (b) occurred before the coming into force of this Act and was not public knowledge before that time - see section 1(4).
Key to this legislation is the existence of Standing Orders of the House. The House of Lords Committee for Privilege and Conduct issued a report containing draft amendments to Standing Orders (Second report Session 2015-16). The amendments are concerned with the process to be adopted before the House gets to the stage of considering a resolution. The matter would be heard by the Committee for Privilege and Conduct and a recommendation would be put to the House. Expulsion or suspension would only be for breaches of the Code of Conduct. The amendments to Standing Orders have been agreed - Motion to agree 16th July moved by Lord Sewel
One aspect of the Code is that Members must always act according to their "personal honour." This term is not defined but the Code states that it is a matter for individual members, subject to the sense and culture of the House as a whole.
Allegations have appeared in the media against Lord Sewel (Baron Sewel of Gilcomstoun) - The Independent 27th July. On 28th July, Lord Sewel's resignation from Parliament was announced. A test of the new Act and Standing Orders will therefore have to await another occasion.
The Sewel Convention is named after Lord Sewel - Telegraph Lord Sewel and the Sewel Motion. The Sewel Convention ensures that Westminster will normally legislate on matters devolved to the Scottish Parliament only with the express agreement of that Parliament, after proper consideration and scrutiny of the proposal in question.
House of Lords - Standards and Interests
House of Lords Commissioner for Standards
Apart from an Act of Parliament (or, possibly, conviction for treason) there seems to no way that a peerage may be removed. The Titles Deprivation Act 1917 was enacted to enable the removal of titles held by the enemy during World Ward 1. Knighthoods and other honours may be removed (e.g. Fred Goodwin) as may membership of the Privy Council though it appears to have been more usual for individuals to request their own removal from the Privy Council as did Chris Huhne in 2013 following his conviction for perverting the course of justice.