Globex applies a band around the last price for each product; an order outside it is rejected rather than executed. Bands are dynamic, widening in volatile conditions and around the open.
Banding is why a mistyped price sometimes returns an error instead of an instant, catastrophic fill. It is a first line of defence, sitting alongside velocity-logic and daily limits.
Example: with ES at 5,000 and a 12-point band, a buy limit entered at 5,100 by mistake is rejected. Entered at 5,006 it rests normally.
Related: velocity-logic, limit-up-limit-down, globex, trading-halt