Could Eru change the very laws of nature if he wanted to?

[Inziladun]

The Fall of Númenor might be considered a pretty substantial alteration in "natural law". We see an island overturned in response to actions of its inhabitants, and a simultaneous removal from the physical world of an entire "continent" when Valinor was transferred to what amounted to a separate plane of existence or dimension.
Also, there was the exchanging of mortality to the reverse that was apparently done to Tuor, a Man.

Originally Posted by radagastly

One has to wonder if, in that same moment, Eru had taken that life back again, whether the Dwarves would have been destroyed by their loss of life, or if they would have gone back to the mindless automatons that Aule built them as at the start?

I would say the latter, since they already "lived" before having the Fire. Being bereft of it should have left them in the same state as previously.