The lawsuit being heard by the U.S. Supreme Court Monday -- U.S. v. Texas -- asks the court to consider whether the president’s 2014 executive actions deferring deportations for some undocumented immigrants are within the government’s authority to direct immigration policy, or whether the president exceeded his constitutional authority by making new immigration laws.
An executive order -- also called the executive power in Article II of the U.S. Constitution -- is a rule or order issued by a president that has the force of law.
U.S. v. Texas focuses on Obama's 2014 program known as Deferred Action for Parents of Americans (DAPA). The program defers deportation for undocumented immigrants who have been in the U.S. since at least 2010, have a child who is a U.S. citizen or is in the country legally, and do not have a criminal record.
The announcement also expanded an earlier deferred-action initiative that applies to people who came to the United States as children, called Deferred Action for Childhood Arrivals (DACA).
Obama said he took executive action because Congress had failed to overhaul the immigration system.
But 26 states, led by Texas, as well as congressional Republicans, are challenging Obama's executive actions. They argue Obama doesn't have the power to effectively change immigration law.
Presidential executive orders are legally binding. Yet if a new administration doesn't like a previous leader's order, it can legally reverse the action.
According to the Federal Registry, Obama has issued 238 executive orders between 2009 and 2016.
President William Henry Harrison, who died just 32 days into office, issued none. While Obama's predecessor, George W. Bush, issued 291 executive orders during his eight years in office.
Franklin D. Roosevelt, who led the country during trying times -- the Great Depression and the start of World War II -- issued the most, with 3,278. Of those, one established internment camps for Japanese-Americans during the war and another created the Works Progress Administration.
For a list of executive orders issued by each president, from George Washington to Obama, visit The National Archives or Federal Register websites.
The National Archives also lists each president's executive actions in alphabetical order.
The White House website also lists presidential executive orders.
Some information for this report provided by the National Archives, Federal Registry, National Constitution Center.