Halakhah do Jozuego 7:1

Or Sameaḥ, Hilkhot Melakhim 3:10, draws attention to Rambam's phraseology in describing the royal prerogative and observes that, for Rambam, the king's extra-judicial penal authority is limited to punishment of infractions bearing upon social welfare; extra-legal punishment for infractions of ritual commandments is reserved to the Bet Din exclusively. This distinction appears to be contradicted by Rambam's statement, Hilkhot Sanhedrin 18:6, in which Rambam declares: "that Joshua killed Achan and David [killed] the Amalekite proselyte on the basis of their own confession was an emergency measure or [by virtue of the] law of the monarchy." Achan's transgression, as described in Joshua 7:1, was a sin against God rather than a sin against society. Rambam's statement regarding the execution of Achan is problematic in any event since those executed by the authority of the king are put to death by the sword whereas Achan was stoned. See Teshuvot Hatam Sofer, Oraḥ Hayyim, no. 208, and R. Rabinowitz-Teumim, Ha-Torah ve-ha-Medinah, IV, 75, note 11. Hagahot Ben Aryeh, Hilkhot Sanhedrin 14:2, suggests that the words "by law of the monarchy" refer only to David's execution of the Amalekite, but not to Joshua's execution of Achan.