The president's power to issue executive orders comes from Congress and the U.S. Constitution. Executive orders differ from presidential proclamations, which are used largely for ceremonial and honorary purposes, such as declaring National Newspaper Carrier Appreciation Day.
Executive orders do not require congressional approval. Thus, the president can use them to set policy while avoiding public debate and opposition. Presidents have used executive orders to direct a range of activities, including establishing migratory bird refuges; putting Japanese-Americans in internment camps during World War II; discharging civilian government employees who had been disloyal, following World War II; enlarging national forests; prohibiting racial discrimination in housing; pardoning Vietnam War draft evaders; giving federal workers the right to bargain collectively; keeping the federal workplace drug free; and sending U.S. Troops to Bosnia.
Historically, executive orders related to routine administrative matters and to the internal operations of federal agencies, such as amending Civil Service Rules and overseeing the administration of public lands. More recently, presidents have used executive orders to carry out legislative policies and programs. As a result, the executive order has become a critical tool in presidential policy making.
Most executive orders are issued under specific statutory authority from Congress and have the force and effect of law. Such executive orders usually impose sanctions, determine legal rights, limit agency discretion, and require immediate compliance. Federal courts consider such orders to be the equivalent of federal statutes. In addition, regulations that are enacted to carry out these executive orders have the status of law as long as they reasonably relate to the statutory authority.
http://legal-dictionary.thefreedictionary.com/Executive+Order