Giving assurance means express an opinion about some information (subject matter) so the users of that information (intendent users) can make a confident decision knowing that the risk of that information being incorrect is reduced.
Regarding audit regulations the only thing that brings to my mind is International Standard on Auditing which provides guidance, regulations and procedures that should be followed by every external auditor. ISAs are promoted by International Audit and Assurance Standard Board (IAASB).