Why will police officers be able to confiscate alcohol from Liverpool fans at the Community Sheild?

Liverpool's official website provided important information for the club's fans travelling to the Community Shield, where there will be drinking zone controls. 

Controlled drinking zone

The area surrounding the stadium is covered by a matchday controlled drinking zone. Fans are advised that police officers or police community support officers can:

Ask a person to stop consuming alcohol
Confiscate alcohol from people, even if the can, bottle or cup is unopened
Dispose of any alcohol and containers in a person’s possession
Fans are advised there are no fan zones at the match; however, there are a number of pubs in the area that have been allocated to Liverpool FC fans.

More Liverpool news: 

Local pubs accepting Liverpool FC fans:

Local Hero - 84 Aylestone Road
Counting House - 40 Almond Road
Symphony Rooms - 121 Burnmoor Street
The Hind - 49 London Road
The Barley Mow - 149 Granby Street
Locker Room - 5-11 Belvoir Street
Walkabout - 21-25 Belvoir Street
Stadium access

Please arrive at King Power Stadium as early as possible to allow sufficient time for necessary search and screening procedures, as well as bag checks. King Power Stadium operates a 100 per cent search policy.

Hospitality turnstiles open at 2pm and general admission turnstiles open at 3pm. Children (16 years and under) must be accompanied by an adult. Children under the age of two will not be permitted into the stadium.