Statement
To save the environment enforce total ban on illegal mining throughout the country.
Assumptions
I. Mining which is done legally does not cause any harm to the environment.
II. Mining is one of the factors responsible for environmental degradation.

Assumption I is invalid because it is not implied that legal mining does not harm and illegal mining does all harm. It is only implied that illegal mining is more harmful for the environment. This happens because in illegal mining norms are flouted with impurity. Only a look on Assumption II gives the idea that it is very much implied in the given statement.