Former US President George W. Bush speaks with First Lady Michelle Obama during an event marking the 50th Anniversary of the Selma to Montgomery civil rights marches at the Edmund Pettus Bridge in Selma, Alabama, March 7, 2015. US President Barack Obama rallied a new generation of Americans to the spirit of the civil rights struggle, warning their march for freedom 'is not yet finished.' In a forceful speech in Selma, Alabama on the 50th anniversary of the brutal repression of a peaceful protest, America's first black president denounced new attempts to restrict voting rights. AFP PHOTO/ SAUL LOEB (Photo credit should read SAUL LOEB/AFP/Getty Images)

Former US President George W. Bush speaks with First Lady Michelle Obama  during an event marking the 50th Anniversary of the Selma to Montgomery civil rights marches at the Edmund Pettus Bridge in Selma, Alabama, March 7, 2015. US President Barack Obama rallied a new generation of Americans to the spirit of the civil rights struggle, warning their march for freedom 'is not yet finished.' In a forceful speech in Selma, Alabama on the 50th anniversary of the brutal repression of a peaceful protest, America's first black president denounced new attempts to restrict voting rights. AFP PHOTO/ SAUL LOEB        (Photo credit should read SAUL LOEB/AFP/Getty Images)