Maybe it has more to do with the joint you share three weeks from now, when you have the job.
Current drug tests detect any marijuana use within the past 30 days; how much does the joint you shared three weekends ago have to do with your ability to do a job today?
Maybe it has more to do with the joint you share three weeks from now, when you have the job.
Maybe ... and maybe not. And how much does the joint you shared Friday night have to do with your ability to do a job the following Monday?
Employers are free to set whatever conditions they want - but if they're restricting the pool of eligible applicants with tests that in some cases have little relationship with job performance, they should reconsider those.