A set of international rules has been worked out for demand guarantees: Uniform Rules for Demand Guarantees (URDG), ICC Publication No. 458.
The rules are issued by the International Chamber of Commerce (ICC) in Paris. They consist of a number of articles dealing with, among other things, the obligations and requirements of the parties under guarantees.
You can obtain a copy of the rules from Danske Bank or the ICC.
It is Danske Bank's experience that these rules are not used widely enough.