If you want something written that actually makes sense, the last thing you want is to have a lawyer write it.

I had a job for two summers during college working for the town doing maintenance. Each year the boss strolled in on day one and told us that we were required to wear long pants and steel toed boots. We nodded and thanked him... then for the rest of the summer we wore shorts and sneakers. He never told us we could wear shorts and sneakers but if one of us got our toes crushed in a horrific accident on the job, he and the town were covered legally.

Policy is one thing. Enforcement is another. The less said, the better (for us).