Players may only be transferred during transfer windows that are set by the Football Association. The two transfer windows run from the last day of the season to 31 August and from 31 December to 31 January. Player registrations cannot be exchanged outside these windows except under specific licence from the FA, usually on an emergency basis. As of the 2010–11 season, the Premier League introduced new rules mandating that each club must register a maximum 25-man squad of players aged over 21, with the squad list only allowed to be changed in transfer windows or in exceptional circumstances. This was to enable the 'home grown' rule to be enacted, whereby the League would also from 2010 require at least 8 of the named 25 man squad to be made up of 'home-grown players'.
Why was this new rule put into effect?
This was to enable the 'home grown' rule to be enacted,

The organizational structure as shown above is responsible for the peacetime organization, equipping, and training of aerospace units for operational missions. When required to support operational missions, the Secretary of Defense (SECDEF) directs the Secretary of the Air Force (SECAF) to execute a Change in Operational Control (CHOP) of these units from their administrative alignment to the operational command of a Regional Combatant Commander (CCDR). In the case of AFSPC, AFSOC, PACAF, and USAFE units, forces are normally employed in-place under their existing CCDR. Likewise, AMC forces operating in support roles retain their componency to USTRANSCOM unless chopped to a Regional CCDR.
What does the abbreviation CHOP stand for? 
Change in Operational Control

The art of writing Chinese characters is called Chinese calligraphy. It is usually done with ink brushes. In ancient China, Chinese calligraphy is one of the Four Arts of the Chinese Scholars. There is a minimalist set of rules of Chinese calligraphy. Every character from the Chinese scripts is built into a uniform shape by means of assigning it a geometric area in which the character must occur. Each character has a set number of brushstrokes; none must be added or taken away from the character to enhance it visually, lest the meaning be lost. Finally, strict regularity is not required, meaning the strokes may be accentuated for dramatic effect of individual style. Calligraphy was the means by which scholars could mark their thoughts and teachings for immortality, and as such, represent some of the more precious treasures that can be found from ancient China.
What is one of the Four Arts of the Chinese Scholars?
Chinese calligraphy