As far as i know, there is no specific regulation for md. of course md ethic do apply. do ask for permission if you want to work on private land/property.
There culd be laws on the relics and coins you find. In Norway (where I live), coins older than 1650 and relics that can be dated older than 1537 must be handed in to the government.
I'm not aware such law. but anything under the certain depth is own by the government, regardless its location. this include crude oil. very different from US law. where you have the right for any oil found in your property.
I googled metal detecting in Malaysia recently because I was thinking of getting in on that action. Found a group who goes around doing it. Give it a google. (I did months ago)
