President Obama issued the Deferred Action for Childhood Arrivals policy in 2012, which allowed children who came to America prior to June 15, 2007 to apply for deportation deferment and for work visas. In 2014, he attempted to extend that law further and to allow other immigrants illegally in the country to apply for deportation deferment and work visas through more executive orders, but, as of mid-2015, those orders have not been implemented due to legal challenges on constitutional grounds.
Immigration reform has been a hot topic, but the largest changes can only come through the legislative process, which is often slow-moving. While immigration reform has been debated by Congress, no comprehensive legislation has passed during President Obama's years in office. The president attempted to reform immigration policy on his own through the development of the Deferred Action for Childhood Arrivals policy, which his administration implemented in 2012.
It is generally accepted that the president has the authority to establish priorities for enforcement of existing immigration law through such policies. However, his additional executive orders in 2014 were considered by some to be overreaching his authority as president by changing substantive law and were thus subjected to lawsuits on constitutional grounds. The U.S. District Court for the Southern District of Texas agreed and found the orders to be unconstitutional. Thus, the additional executive orders have not been implemented.