In any organisation technically nobody has power to do whatever he or she wants, even the CEO needs to answer to the Board of Directors even if that board of directors are "figureheads".
If LaPierre is spending organisation money on himself I find it hard to believe that the board was not aware of his spending habit and if they weren't than they didn't perform there duties.
LaPierre is not a coffee boy but the top dog within the NRA.