case block

One who prevents the person or persons they are hanging out with from getting free alcoholic beverages, sometimes in the form of a case of beer, from an interested suitor. The suitor refrains from delivering the beverages because they believe they would be cock blocking the case blocker.

Mary: "I was going to get shit-faced for free off of that guy's 30 pack of Bud Light, but Randy definitely case blocked me from scoring any by sitting next to me."