Yesterday, Veterans Day in the U.S., President Obama attended a ceremony in Arlington National Cemetery. Here is is pictured at the Tomb of the Unknown Soldier. The President is standing with his hands-clasped in this very familiar "Fig-Leaf" formation. While the fig-leaf usually is a signal of low confidence - in some contexts it certainly indicates other emotions. One is respect and another is reverence. These are two leadership-appropriate messages a President or Head of State should desire to convey using the fig-leaf.
So when is it appropriate for a President to Stand in the "Fig-leaf"? Very few times. One example is a funeral or a ceremony to honor those who have died serving in the military - as pictured above. Another is at any religious service. If he were meeting with the Dalai Lama, the Pope or another high religious leader he/she may want to adopt this pose as well - even if there was no service or ongoing religious activity. If a past-president or head-of-state was standing next to the current equivalent leader at a ceremony or introduction, the former leader may want to use the fig-leaf here as well. Weddings are another venue for the fig-leaf.
With these few exceptions, and perhaps a few other respect-reverence scenarios which I have omitted, a head-of-state should never stand in the fig-leaf pose, lest he/she convey low confidence. A head-of-state should not adopt this pose around other World leaders if he/she is to command respect (unless of course at a funeral, etc. as detailed above). It will certainly place them at a leadership and negotiation disadvantage. Moreover, standing this way will even change your physiology and actively lower one's confidence. Nonverbal signals are indications of what the emotional brain is feeling in real-time, and maintaining the body language will engender and reinforce the emotion.