I believe the law is very clear in that any employer may regulate carry while you are working for them. I believe it's equally clear that an employer may not regulate car carry. I'd be careful if I were you in dealing with this with your employer.
I don't know if a lawyer knowing gives incorrect information is illegal, but I'm sure it's against the bar and they would at the very least receive a reprimand. Perhaps you should sit down one on one with him and calmly discuss this policy. I would also ask to see the policy in writing.