Combat Patrol and Charge

Question

I have a level 10 Orc Fighter. Among other things, I have the Combat Patrol feat.

As a full-round action, you may set up a combat patrol, increasing your threatened area by 5 feet for every 5 points of your base attack bonus. Until the beginning of your next turn, you may make attacks of opportunity against any opponent in this threatened area that provokes attacks of opportunity. You may move as part of these attacks, provided your total movement before your next turn does not exceed your speed. Any movement you make provokes attacks of opportunity as normal.

I set up my Combat Patrol, in front of our bard. An enemy attempts to charge that bard.

Charge
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You must have a clear path toward the opponent, and nothing can hinder your movement (such as difficult terrain or obstacles). You must move to the closest space from which you can attack the opponent. If this space is occupied or otherwise blocked, you can’t charge. If any line from your starting space to the ending space passes through a square that blocks movement, slows movement, or contains a creature (even an ally), you can’t charge. Helpless creatures don’t stop a charge.
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As part of the attack of opportunity I get, I'm allowed to move due to Combat Patrol. I stand in front of the charging enemy as part of my Attack of Opportunity. Does this stop/interrupt the charge?

On one hand, the action is already on-going, and even if it's just my limited knowledge, I don't know any other case where an on-going action is invalidated. (Even counterspells just negate the spell, but don't interrupt the action of spell-casting.)

On the other hand, that path is still blocked by 234 lbs of Orc Fighter, and at the very least, that would have prevented the enemy from starting that action at this moment.

Answer 1

Actions can be interrupted. After all, instead of your orc with Combat Patrol, the enemy could have charged across a hidden pit trap and fallen in—definitely not going to continue their charge in that case.

In this case, they could not have charged your ally if you had been in that location the whole time. Thus, they cannot charge that ally now that you have moved there. Quite simply, they cannot meet the charge’s requirements.

There are some concerns, however. The first and most obvious is, can they now attack you? Assuming your intercept occurs after they have moved at least 10 feet, you would be a valid target for a charge—at least, you would if you had been there the whole time. Or what about a non-charge attack? If they have only traveled five feet, that could even look like a possible full-attack.

These questions are unanswered. The rules don’t get into strict rules about when you are committed to particular actions very often. When they do, they are sometimes explicit about you being committed (e.g. readied actions) or about you being free to change your mind (e.g. deciding between attack or full-attack after your first attack), so we can’t even get a good sense of what the default is.

The full-attack, at least, we can be pretty confident is not possible. Full-attacking at that point requires that your only movement was a 5-foot-step, which they obviously didn’t take since you were provoked.

Continuing a charge is less clear, but I lean towards that not being possible either. Charging requires seeing your opponent—you can’t just charge in some direction and attack the first thing you come across. That implies that the charge maneuver is greater than the sum of its parts, that you need to be timing your charge attack ahead of time. No sudden change of plans there.

Just a regular attack, though, I would allow unless they have already moved more than their speed. The case against it is that the enemy attempted a full-round action, and now no longer has anyone with which to attack. But since they haven’t attacked, and haven’t moved more than they could with a simple move action, I rule that they have not actually completed a full-round action, and have not used up their standard action yet. The rules are very much silent on this subject, however; they do not specify “when” an action is used.

The other concern I would have is whether they can use an ability that would allow them to charge through you. Off the top of my head, I cannot think of any such abilities, but it is plausible that some may exist. Since this is hypothetical, however, I have no rules to consider against this situation—whether or not it would be allowed would depend on the wording of the ability.