Rather, the key point he made was that setting a quantitative,...

Rather, the key point he made was that setting a quantitative, and therefor arbitrary, limit, is the wrong way to go.
Distance from population centers is, in this way, in itself, also arbitrary.

IMO, the best way is to take each EIA on its merits, and judge it on its scientific and engineering, fact-based aspects, including recognizing the opinions of industry-recognized geological and environmental experts where appropriate.
Built in to an EIA, but not as determining criteria, will be matters like distance from population, predicted radiation levels, etc.

Greenland's Mineral Resources Act, or whatever it is called, probably already defines this adequately.