What must occur in society for established law to change

In order for an established law to be changed, the citizens usually have to vote for the law. This voting goes through the House of Representatives and the Congress before being sent to the Executive (The President). Up until this point, it is considered a Bill. The President has the power to Veto or Accept the Bill. If he decides to veto it, the Bill is killed. If it is Accepted, it will become a law.