In the United States, Executive Orders are issued by the President and are legally binding. They have the same power as laws that are passed by Congress. However, they don't require approval by Congress in order to be enacted.
Executive Orders seem to nullify the rights given to Congress by the U.S. Constitution because they leave Congress out of the decision making process, and appear to concentrate power in one place. However, Congress is not totally impotent when it comes to EOs. Congress can vote to override an Executive Order, or they can challenge it in court.