When the Detroit Lions used a seventh-round draft pick on Army safety Caleb Campbell in April, Department of Defense policy allowed West Point graduates to avoid active military service if they had the ability to become professional athletes.

Now the Department of Defense has changed that policy, and Campbell will not be able to play for the Lions.

U.S. Army Lt. Col. Jonathan P. Liba wrote a letter to Lions president Matt Millen today, saying Campbell has been ordered to give up football for “full-time traditional military duties.”

Under current Department of Defense policy, Campbell will be eligible to request release from his active duty obligations in May 2010. At that point, he would have to reimburse the Army $120,000 for his West Point education and enroll in a reserve unit for six years.