Well, the wording is important here: OHASAS 18001 4.5.2 calls for evaluation of compliance (Reference guidance document here:http://www.imsworld.org/blog/wp-content/uploads/2010/10/EA-7-04.pdf ). But basically you have to demonstrate independent third-party (Certification Body) has evaluated and confirmed that the organisation has a demonstrably effective H&S to ensure the fulfilment of its policy commitments including legal compliance. So in a nutshell external audits, which in short verify that you have met the criteria need by the standard (Risk assessments, management review etc the whole shabang. Long winded but hope it helps

Pad PM me with your email and I will send you our compliance procedure and example compliance register. Simply put you list your statutory obligations, provide evidence as to compliance (internal procedure, permit, other, etc) then show how you check that the process works, internal audit, inspection etc.