[dlgeek]

It's also about the ability to follow rules (arbitrary or not). If you can't be trusted to follow the rules about not doing drugs, why should they assume you can be trusted to follow the rules about protecting classified information?

(That represents my understanding of the clearance processes' view of the issue, not my personal beliefs).

[jfoutz]

My, very shallow, understanding is, people can’t follow rules. There are a few rare individuals that can, but not the tens of thousands that are required.