Lady Justice has tossed aside her blindfold and tipped her scale. A border-crossing drug smuggler walks free while the officer who arrested him has been jailed. In the age of Obama, the law has been turned upside down. U.S. Border Patrol Agent Jesus E. Diaz Jr. is set to spend the next two years behind bars after being sentenced last month for what the Justice Department called deprivation of an illegal-immigrant suspect’s constitutional right to freedom from the use of unreasonable force. The unnamed Mexican suspect, who was 15 at the time of his arrest in 2008, received immunity from...