You shouldn’t be denied for smoking weed in college and disclosing it. I had no issues with that. The other thing is you can appeal a denial of your clearance if you can demonstrate the issue is not an issue. If you truly did only smoke weed in college and get denied due to that, you could appeal and make your case that your weed use is not ongoing, ended in college, and not an issue in your personal life. It’s not guaranteed to be a successful appeal, of course, but the process does exist.

The bigger problem is when people fib about their usage. Saying you only used it in college when you’ve used it more recently is something people do fairly often, and seemingly are encouraged to fib about.