Obama is only returning part of the money raised by family of person who is linked to violence and corruption in Mexico and seeking pardon

So if the family can convince others to give money to Obama's campaign, that money can be used by the campaign? Why not return it and let the individuals re-donate it if they want to give the money? From the Canadian National Post:

President Barack Obama’s re-election campaign is returning more than $200,000 in donations from the family of a fugitive casino magnate linked to violence and corruption in Mexico who has been seeking a pardon, Obama’s campaign confirmed on Tuesday. . . . .
The New York Times cited Obama campaign officials as saying that said most of the donations of about $200,000 came from the Cardonas brothers themselves and other relatives. The campaign was identifying other donations, believed to total less than $100,000, that was bundled from other people, the newspaper said. . . .