Ukraine
In Ukraine, the imperative mandate provision of the Ukrainian Constitution banned party switching in Parliament from 2004 till 2010. The mandate stipulated that the constitution and laws of Ukraine obliged members of the Verkhovna Rada (Ukraine's Parliament) to remain members of the parliamentary faction or bloc in which they were elected. This was evident during the 2007 Ukrainian political crisis where members of the opposition crossed party lines with plans to undermine Presidential authority and move towards the 300 constitutional majority.
Read more about this topic: Party Switching