Rebuffed this month by skeptical lawmakers when it sought finances to buy a prison in rural Illinois, the Obama administration is struggling to come up with the money to replace the Guantánamo Bay prison. ... Frustrated by the difficulties in obtaining financing from Congress, administration officials had discussed invoking a little-known statute that would allow the president to declare a national emergency and then use military funds allocated for other construction projects to buy and retrofit the Illinois prison. That statute, however, has never been used for a project quite like this one. Fearing that lawmakers would be angered by...