Assuming there is some correlation between illegal substance use/abuse, the test could be used to identify people with underlying issues that affect their work.

Assuming there is some correlation between illegal substance use/abuse, the test could be used to identify people with underlying issues that affect their work. No one really cares about your personal life, just use that as a proxy for your ability and risk mitigation. If it doesn't affect your work and you are a strong performer, the test results are not enforced. I think this is a reasonable response.