Sometimes effective public diplomacy can be conducted through a simple and unambiguous gesture. Such was the case when President Barack Obama recently commemorated the 50th anniversaries of 17 African nations’ independence at the White House. The gesture – or really a non-gesture – was to not invite a single African head of state to the event.

Given the dismal performance of some African leaders, such as Zimbabwe’s Robert Mugabe, Obama chose to celebrate instead with 115 Africans under age 35 who are working to shape the continent’s civil society of the future. By doing so, he underscored a point he made in his speech in Accra, Ghana a year ago: “Africa doesn’t need strongmen; it needs strong institutions.”

The White House event was a very visible slap at the “strongmen” Obama had criticized, and it was noticed in Africa. Adam Nossiter, reporting from Senegal in The New York Times, observed that a Senegalese newspaper remarked on the absence from the White House of that country’s controversial president, Abdoulaye Wade, and said that Obama “unrolls the red carpet for civil society.” A Cameroonian newspaper, wrote Nossiter, featured a headline saying, “Barack Obama Snubs the African Dictators.”

Other African news media echoed these sentiments, and Internet forums buzzed with comments about Obama’s stance. If public diplomacy involves reaching out to people rather than to governments, this was an excellent example. In terms of illustrating America’s commitment to democratic governance, Obama’s choice of guests sent a clear message, which he knew would be conveyed by news and social media to the larger African public.

Obama reinforced this in his discussion with the young visitors. He said: “Sometimes the older leaders get into old habits, and those old habits are hard to break. And so part of what we wanted to do was to communicate directly to people who may not assume that the old ways of doing business are the ways that Africa has to do business.”

Underscoring Obama’s point about “the old ways” of doing business was the assemblage at a Bastille Day celebration in July in Paris. There, 13 African heads of state joined French president Nicolas Sarkozy on a reviewing stand. The contrast was striking: these African leaders, some of whom have been sharply criticized for human rights abuses, stood with the leader of a former colonial power that had subjugated large parts of their continent. Meanwhile, the next generation of what will be, one hopes, more enlightened African leadership was invited to the White House.

It wasn’t so much what Obama or Sarkozy said that delivered their respective messages, it was what they did. Their guest lists were public diplomacy.