Abuse of central nervous system (CNS) stimulants is common. Addiction to some CNS stimulants can quickly lead to medical, psychiatric, and psychosocial deterioration. Drug tolerance, dependence, and sensitization as well as a withdrawal syndrome can occur.
The judicial branch decides what amendments are unconstitutional as well as acts of the president. However, if the judicial branch were to declare an act of the president unconstitutional, it would mean that Congress agreed to this act.
They can't just declare any law unconstitutional. Someone (a citizen or the government) must sue in court, and that case must be appealed until it reaches the Supreme Court, which may then accept the case and decide what the Constitution says about the principle at issue in the case.