dnd 5e – When a spell that clouds the target’s judgement is cast on a player character, how can I make sure they act accordingly?

Enemies Abound causes no loss of judgement except for what the spell description indicates.

Yes, Enemies Abound says that it causes the target to “consider all creatures it sees as enemies,” but that has no gameplay effect except for having to “…choose the target at random from among the creatures it can see within range of the attack, spell, or other ability it’s using,” as well as taking opportunity attacks no matter who provokes them. All other behavior is fair game.

Sure, this may involve players finding loopholes. Perhaps the Ranger that you cast Enemies Abound on tosses down her bow, takes out a sword or two, and runs into melee combat with the bad guy to reduce the possibility of hitting a friendly, but there’s nothing preventing that. Which leads me to the answer of the larger question…

Loss of agency is no fun. Let the players play with the boundaries.

Nobody likes being stunned, incapacitated, puppeted or Suggestion-ed. So, when the dice go your way and the enchantment lands, define their new limitations well, but don’t worry about them “finding a way around it.” You’d probably want to find the exceptions and loopholes in the instructions yourself, particularly if you were playing a canny villain or nasty genie.

There’s few situations in which the loophole would lead to a complete negation of the spell, in any case. In my above example of the ranger, sure she’s no longer in danger of feathering allies, but she is in melee now, which might be less preferable. As another example, if a wizard was Suggested to “attack the ranger,” perhaps he’d take out his dagger and attempt to stab her–certainly a less effective means of attack than his spells, but it’s completely within the bounds of the Suggestion, and still takes the wizard out of the offensive fight for a turn or two.

Allow the player to remain in control of their characters as much as possible, make the rules clear, and see if they get creative.