The hotel-casino has a drug policy for legal and/or PC reasons. That policy probably requires that violations be reported to authorities. It wouldn't be PR [not PC] correct to tell people "Violation of the 'NO DRUG' policy must be reported." That would drive off potential customers in an industry that's hurting for occupants. Instead, they awkwardly word it "
Violation of the 'NO DRUG' policy must be adhered to." meaning that violations must be reported in adherence to policy. Thus, the house rule becomes more of a curiosity than a threat. The approach works if your introductory post is any indicator.
