It's not so easy, it turns out, for Congress to sue the president. Speaker John Boehner is finding that out the hard way after a second law firm withdrew from representing the House in the Republican-led lawsuit against President Obama over his use–or overuse–of executive authority. William Burck of the Washington-based firm Quinn Emanuel pulled out of the case last month, not long after he signed a contract with the House to replace David Rifkin of BakerHostetler.