“The law doesn’t prohibit driving under the influence of (prohibited) intoxicating drugs”:

Correct. The law only prohibits driving under the influence of alcohol.

Incorrect. It is explicitly prohibited by the law to drive under the influence of intoxicating drugs.

Correct, since the law doesn’t prohibit the use of intoxicating drugs.

Incorrect. The law explicitly mentions that it is prohibited to drive under the influence of a certain quantity of intoxicating drugs in the driver’s blood.