This happened in January 2012. The two British tourists – Leigh Van Bryan and Emily Bunting were banned from the USA, because they were previously flagged as a potential threat by the Department of Homeland Security. The reason for that was because they joked on Twitter how they are going to “destroy America” (meaning to party) and to ‘dig up Marilyn Monroe’ (actually a quote from The Family Guy show).
So, when they arrived in the USA, they were arrested by federal agents, who searched their bags and than sent them to jail for 12 hours (in different cells). After that, they were put on a plane to UK (via Paris).