The force field protecting Jirayut Latthivongskorn comes from a glossy, federally issued work permit that wards off deportation and lets him get a job, overcoming the legal barriers that have long clouded his ambitions and shadowed his life. Mailed to homes in fast-growing numbers, the cards are changing the lives of about 300,000 young immigrants, a quarter of them from California, who took a leap of faith this fall by revealing their presence to the U.S. government. Latthivongskorn's plastic card, with its 2014 expiration date etched between his fingerprint and photograph, symbolizes what he calls his "two-year lease on life...