As President Obama moves forward with his plan to shield millions of undocumented immigrants from deportation, an existing program to protect young illegal migrants demonstrates the life-changing promise of executive action but also its profound shortcomings, according to experts and government documents.

◼ Obama’s 2012 DACA move offers a window into pros and cons of executive action - Jerry Markon and Sandhya Somashekhar/Washington Post

The 2012 initiative has given temporary protection to slightly more than 700,000 people brought to the United States illegally as children. They say that program has helped them emerge from the shadows, making possible a work permit, a Social Security number and enhanced self-respect.

But hundreds of thousands who advocacy groups say are eligible have not applied under the program, known as Deferred Action for Childhood Arrivals, or DACA. Some immigrants say they are afraid they will be rejected and deported, while others are daunted by the $465 application fee and educational requirements. Still others remain unfamiliar with the program because of language and cultural barriers.