Can an employee on off sick enter the employer's premises to access a document which can only be accessed from work (like a trusted document e.g.: Occupational health report) or to get some documents from the personal locker and return quickly?
If you are on sick leave and you go to the office, the company may have problems with the law enforcement authorities. It can be interpreted that they forced you to come to work while you were sick.
Also, it depends on why you are on sick leave. Is your sickness contagious? If yes, it is a risk for the other employees. Can your health further deteriorate because of the effort to go to office? The company surely does not want this.
So yes, there are several reasons why an employee should not visit the office while on sick leave.
Discuss the situation with your superior (probably on the phone) and find a solution which is mutually satisfactory.
As someone who has gone to the workplace while sick, I can tell you that the company asked me to leave, because I was violating the company's insurance policy. I believe, that if something were to happen while I was there, then the company could have had difficulties with the insurance company, even though I was just collecting something from my desk. If in doubt, check with your legal department.
If you are on leave, they may, for reasons of liability, want to keep you off the premises, depending on how obnoxious the agencies are in enforcing labor laws to the letter.
The way around this is to send a representative on your behalf. There is no justification for them barring an authorized representative.
A call should precede the visit and should come something like this
Hi, this is Maria Paul. I need something from my locker, I'd like to send my brother in to retrieve it for me. Is later today good?
Obviously, they may want to schedule a time, but they have no right to bar you from getting your things.
seems a little extreme to ban someone from the premises while they are sick. personally i would have no problem if a sick worker came into work for a legitimate reason (like the examples you listed) but it was made clear that they were not there to work and they were off for a reason. its possible that coming in for any reason while sick is against your companies CoC but i cant really see a decent reason why (unless they were contagous but that really shouldn't be an issue if the person is there for 5 minutes to get something from a locker or desk)