The guest list must be approved by the Queen
At a royal wedding, the guest list is carefully compiled by the couple and their staff and approved by the Queen. In William and Kate’s case, 1,900 invitations went out by Her Majesty’s command to members of the royal family (but not banished black sheep Sarah Ferguson), foreign leaders, and celebrities including David and Victoria Beckham, Elton John, Guy Ritchie, and Joss Stone, in addition to the couple’s own friends and Kate’s family.
For Harry and Meghan’s wedding, the official word is that the couple decided to focus on family and friends and decided not to include politicians, including Prime Minister Theresa May. If we had to guess, we’d say it was exceedingly difficult for Harry to cross off his good friends former president Barack Obama and Michelle Obama from the guest list, but in order not to wade into the current choppy political climate, he was persuaded by someone (ahem) at the top.