Well unfortunately you as the employer would have to put up with the fact that the inconvenience you may have to endure as a result of lacking the right to snoop around and invade the privacy of your staff is trumped by the right of your staff and prospective staff to privacy (in most cases).
Lot's of things may affect worker productivity. Smoking, drinking alcohol, having a poor diet, failed relationships, chronic insomnia, being a young woman (and therefore probably wanting to have kids in the near future), pre-existing medical conditions, etc etc . Most of these fall well within the private sphere. Are you seriously suggesting that an employer should have the right to insist on screening for all of these things ?
Also, we aren't just talking about the process of hiring. In the main drug testing would be carried out on existing members of staff. In that circumstance an employer would already know full well how they were performing in the job. If you have a member of staff who's performing fine that you're happy with then why do you care if they smoke a little dope at the weekend ? What business is it of yours ?
Lot's of things may affect worker productivity. Smoking, drinking alcohol, having a poor diet, failed relationships, chronic insomnia, being a young woman (and therefore probably wanting to have kids in the near future), pre-existing medical conditions, etc etc . Most of these fall well within the private sphere. Are you seriously suggesting that an employer should have the right to insist on screening for all of these things ?
Also, we aren't just talking about the process of hiring. In the main drug testing would be carried out on existing members of staff. In that circumstance an employer would already know full well how they were performing in the job. If you have a member of staff who's performing fine that you're happy with then why do you care if they smoke a little dope at the weekend ? What business is it of yours ?