In more populated stretches of the 2, 000 mile (3, 200km) border, in California and Texas, long fences have been built and extra Border Patrol agents deployed.

ECONOMIST: Mexico's northern border

They will not be empowered to arrest anyone, and they will be withdrawn after a year or so, as the promised extra Border Patrol agents are trained and deployed.

ECONOMIST: Immigration

In past decades, schools have installed metal detectors, hired extra security to patrol grounds and hallways and instituted other zero-tolerance measures to make campuses safer.

CNN: How to deal with guns in school

London's Metropolitan Police said as many as 6, 000 extra officers were on patrol during jubilee events.

CNN: Eyes of world on spectacular Thames royal pageant