Well, regulations are regulations. even if i am pretty sure that a moose drops dead on a encounter with a .45-70-405 ( .45-70 Government, 405 grains solid round nose lead bullet) that crawls along at 1,394 ft/s.
But it does not have the minimum legal energy.
And if you are caught hunting big game with a cartridge that does not meet the minimum legal energy, well.. Goodbye Mr. Hunting license.
It is required that a cartridge/load does can be proved to meet the minimum energy levels.
A .54 Muzzle-loader can do that, and are legal in Norway
The problem is the reload time.