President Obama's deep bow to Japanese Emperor Akihito on Saturday may not have violated any official protocol, but critics of the presidential act of deference nevertheless say he's guilty of bad form.

The incident followed Obama's dip to King Abdullah of Saudi Arabia in April, which the White House said was not a bow despite the criticism that followed.

But in Japan, the White House could not argue with a photograph that showed him bent at a nearly 90-degree angle while shaking the hand of the emperor, as Empress Michiko smiled faintly next to him.

Instead of denying the gesture, an administration official defended it, telling Politico.com that Obama "observes protocol" and that the greeting "enhanced both the position and the status of the U.S. relative to Japan" -- where a bow is just another version of a handshake.

But 'protocol?'

Pamela Eyring, the president of The Protocol School of Washington, said that while there's no "hard-and-fast" rule, a bow is not appropriate when national leaders meet.

"They're peers. ... Unfortunately, it isn't correct for a chief of state to bow to another chief of state," she told FoxNews.com. "It's not appropriate. He should not be bowing to other chiefs of state."

She said Obama was clearly trying to show respect, but that the royal couple would not expect such a gesture from a Western leader. Eyring, who reviewed the video of the encounter, said they seemed a "bit uncomfortable" watching Obama bow.

"When you're representing the United States of America, everything speaks ... on behalf of our country," Eyring said. "It's a visual. It shows more of a subservient look."

By most accounts, it hasn't been official protocol for a U.S. president, or any American, to bow to a foreign head of state or symbolic monarch. Other heads of state and officials, like former Vice President Cheney, have greeted the Japanese emperor with a handshake -- which Eyring said is the appropriate custom.

Former President Clinton got slammed for coming close to bowing to the Japanese emperor in 1994. The New York Times ridiculed him, noting, "The image on the South Lawn was indelible: an obsequent President, and the Emperor of Japan." But the paper wrote that the "thou need not bow" standard in State Department protocol has been constant since the country's founding.

Even "Miss Manners," while perhaps not the guiding force for the president's travel team, wrote two decades ago that, "One does not bow or curtsy to a foreign monarch because the gesture symbolizes recognition of her power over her subjects."

Following the encounter with the Saudi King, The Washington Times declared it a "shocking display of fealty" and an "extraordinary protocol violation."

Likewise, Obama's latest bow has critics fuming. One blogger called the act "treasonous."

And a headline in a Los Angeles Times blog asked: "How Low Will He Go?"