In Employment Div., Oregon Dept of Human Resources v. Smith, what is the key limitation recognized by the Court regarding when an employee at a drug rehabilitation center can legally be fired from their job for using a controlled substance, even when that person was using that controlled substance as part of the free exercise of his religion?

A. The First Amendment protection of the free exercise of religion does not extend to protect any specific religious practice, such as the use of peyote in certain Native American Traditions, because most people do not approve of drug use.

B. The First Amendment protection of the free exercise of religion does not extend to protect the use of peyote in a drug rehabilitation center.

C. The First Amendment protection of the free exercise of religion does not extend to protect drug use of any kind.

D. The First Amendment protection of the free exercise of religion does not extend to protect against the violation of a federal law, such as the use of peyote, which is a prohibited controlled substance.