It depends on what you mean by 'legal document'. If you mean a document that could be required and be relied on as evidence in court proceedings - then yes. But in this sense, any relevant document can be a legal document. If you mean a document that has been prepared or approved by lawyers, then clearly not. If you mean a document that you are legally required to have, then no - it's your internal system that is setting the requirement. It may help you comply with broader legal duties, or to demonstrate that compliance, but there's no specific legal duty to have a permit. If you mean a document that results in a legal requirement for someone to do something, then no. It's the internal system's requirement, again, that they do it. Of course the people involved do have legal duties eg to work safely, to cooperate, and so on, which might imply doing as the permit says, but there isn't any specific legal duty to do with permits especially. Requirements to do with permits might be in the terms of a contract, but then it's the contract that's the legal document. What do you have in mind here?

I'm not sure I fully understand the question but would point you in the direction of the HSE document 'HSG250 - Guidance on permit-to-work systems: A guide for the petroleum, chemical and allied industries': http://www.hse.gov.uk/pubns/books/hsg250.htm This defines the role of the Permit, and although aimed at petroleum, chemical and allied industries, it is relevent to any company that uses permit to work systems i think. Hope this helps Alan

Kate's comments are spot on, Permits are part of your control measures, and is a way of ensuring that every thing is in place before the work activity starts, legal use, would be used in your defence