As of Oct 29, 2014:

• 3.1.1 The pack is defined by the largest group of in-bounds and upright Blockers in proximity and containing members from both teams.
• 3.1.1.1 Jammers are not part of the pack.
• 3.1.1.2 Proximity is defined as not more than 10 feet (3 meters) (as measured from the hips) in front of or behind the nearest pack skater.
• 3.1.1.3 In order to form a pack, a team must have at least one Blocker on the track at all times.
• 3.1.2 When two or more groups of Blockers equal in number are on the track, are more than 10 feet (3 meters) from one another, and no single group meets the pack definition, no pack can be defined. Skaters will be issued a penalty for intentionally creating a No Pack situation, or destroying the pack (see Section 5.10.2). Both teams are responsible for maintaining a legally defined pack. A skater or group of skaters is always responsible for the consequences of their actions. If their actions create a No Pack situation (except those covered in Section 5.10.2.3), they should be penalized as directed in Sections 5.10.11 – 5.10.21.
• 3.1.2.1 Distances for determining the pack and the Engagement Zone are measured as the shortest distance parallel to the inside track boundary between skaters’ hips (see Glossary for Hips).