I just located the most recent version of the Wells Fargo Employee Handbook. This is what the section on drugs states:

Wells Fargo is dedicated to maintaining a drug-free workplace. All our team
members are required to perform their job duties unimpaired by illegal drugs,
alcohol, or the improper use of legal substances. You are prohibited from
working or reporting to work when impaired by alcohol or drugs.
Important: Any team member who is unfit to work because of alcohol or drug
use may be sent home. In addition, he or she is subject to corrective action,
which may include termination of employment.

Drug-free Workplace

We have absolutely no tolerance for illegal drugs ā?? or the misuse of legal
drugs ā?? at Wells Fargo.
Important: The sale, purchase, manufacture, distribution, possession or use
of any mind-altering or non-prescribed controlled substance, or the nonprescribed use of a controlled substance, on company premises or while
conducting company business is prohibited and is cause for immediate
termination of your employment. In addition, illegal substances found on
company premises may be turned over to outside legal authorities for
further investigation.

From what I can read there is no mention of a drug screen, just if you are caught being impaired on the job you're in trouble. Thoughts?