Thou shalt not transgress the carrying capacity
In a finite world this means that the per capita share of the world's goods must steadily decrease.
You can never do merely one thing. The law applies to any action that changes something in a complex system. The point is that an action taken to alleviate a problem will trigger several effects, some of which may offset or even negate the one intended.
Every plausible policy must be followed by the question 'And then what?'
You cannot do only one thing.
A coldly rationalist individualist can deny that he has any obligation to make sacrifices for the future.