An obscure but important court that oversees security-clearance disputes with government contractors uses a deeply idiosyncratic process, with few hard and fast rules, a review of its decisions reveals.

Following the Washington Navy Yard shootings by defense contractor Aaron Alexis last week — and leaks by contractor Edward Snowden earlier this year — a chorus of critics wants to know how the two men both passed supposedly rigorous background checks. President Barack Obama last week ordered a review of federal policies for granting security clearances; Defense Secretary Chuck Hagel said the department would review its protocols; and four U.S. senators called for an independent investigation.