Interesting, and odd, turn of events. From Ambinder at TIME – well, Pete Williams apparently first reported this:

Article One, Section Six of the U.S. Constitution says:

No Senator or Representative shall, during the Time for which he was elected, be appointed to any civil Office under the Authority of the United States which shall have been created, or the Emoluments whereof shall have been increased during such time; and no Person holding any Office under the United States, shall be a Member of either House during his Continuance in Office.

Essentially, you cannot take a job if the salary was increased during your current congressional term. And the salary for cabinet officials has gone up in the past year. Even if it is lowered back down, constitutional scholars say that may not be enough to fix the problem.