Regna's Sanction

The designation of friend or foe is only relevant to the spell that asks you to choose. A player you call your friend doesn’t become your teammate, and the next “friend or foe” spell you cast could name that player your foe.

When Regna’s Sanction resolves and your foes perform their actions, first the next foe in turn order (or, if it’s a foe’s turn, that foe) chooses an untapped creature they control, then each other foe in turn order does the same, then all other creatures those players control are tapped at the same time. Foes will know choices made by earlier players when making their choices.

Friends perform their specified actions before foes. This means that a friend’s action may cause a triggered ability of a foe’s permanent to trigger before that foe’s action causes that permanent to leave the battlefield.