When the Sri Lankan Prime Minister Mahinda Rajapaksa got the unanimous approval of his parliamentary group for legislation to ban cow slaughter, it was not the first attempt to have the practice banned. Despite toying with the idea of banning cow slaughter from time to time, no government has thought it fit to legislate on it.
This is probably because cow slaughter is entangled with larger issues, which have been religious, social, economic and political. Of these, the most important one has been Buddhist-Muslim relations. The cow slaughter issue has tended to come up when these relations are strained, and brushed under the carpet when they are fine.