In my neck of the woods, if you enter a court facility the deputies make you empty your pockets, and metal scan you.
But beaches, parades, stadiums rely on very little in the way of scrutiny of those that might try to commit mass harm on innocent folks enjoying their holiday.
Huntington Beach hosts the largest July 4th Parade, west of the Mississippi, and it would be a perfect target for an attack like the Boston Marathon.
1914
2013