I am going to have my party face level 7 orc fighters mounted on worgs. I gave them leap attack, shock trooper and ride-by-attack. Can the orcs use their leap attack feat and the heedless charge option of shock trooper while mounted - i.e. does it work if the mount leaps to trigger leap attack and can the orcs take the penalty of power attack to their AC even if they charged on a mount (that does not have shock trooper)?
A mounted rider can't charge, yet the rider's mount can...
The rider's riding a mount, and, when the mount moves, the rider moves because the rider's atop the mount. If the rider wants to charge someone, the rules say the rider has to meet the requirements of the charge, and that includes the rider moving at least 10 ft., and the rider hasn't moved 10 ft. even if the mount has.1 Likewise, this DM wouldn't let a rider make an overrun attempt. I mean, really, the rider's on a mount, so the mount has to barrel through foes. And, while the mount itself could benefit fom Leap Attack and Shock Trooper, the rider can't until the rider dismounts.
Further evidence for this comes from the Player's Handbook in its description of the lance, which says, "A lance deals double damage when used from the back of a charging mount" (118). And from Charge, which says, "A lance deals double damage if employed by a mounted character in a charge" (155), language vaguer than necessary for what could've been a more obvious statement. And from Mounted Combat, which says that
If your mount charges, you also take the AC penalty associated with a charge. If you make an attack at the end of the charge, you receive the bonus gained from the charge. When charging on horseback, you deal double damage with a lance. (157)
That's all one paragraph, by the way, implying that that charging on horseback is shorthand not for the rider actually charging but for the rider benefiting (and suffering) from his mount's charge.
...Or, then again, maybe the rider can charge, too
After puzzling over the mounted combat rules again, there's enough to add a counterpoint. Honestly, the mounted combat rules are opaque, and the notion above is disempowering.
- A Ride check (DC 10) to fight with warhorse means the rider "can still make [its] own attack or attacks normally" (80).2 "Charging" according to the Player's Handbook, "is a special full-round action" (154), not just an attack or attacks. The DM would have to rule that a charge can be executed while mounted. (This would also require a mount trained in combat riding.)
- Unlike the statement that opens this answer, the Player's Handbook on Mounted Combat says, "Your mount acts on your initiative count as you direct it. You move at its speed, but the mount uses its action to move" (157). So the rider's mount's movement is the rider's movement, hence satisfying one requirement for executing a charge.
- I don't know what to do about the mount and the rider sharing the mount's space and, in the case of a charge, what exactly that means for having a clear path. ("For simplicity, assume that you share your mount’s space during combat" (157).) The DM would have to rule that a mount doesn't interfere with the rider's own charge, which is fairly reasonably as, after all, a rider doesn't interfere with a mount's charge.
All of these point to the core rules possibly allowing a mounted rider to execute a charge, even if his mount doesn't.3 The FAQ agrees, including this exchange:
What are the rules for mounted charges? Do characters on mounts need only a 10-foot straight path when charging? Or do they need more room?
The rules for mounted charges are the same as for other charges. You must move before your attack, not after, and you must move at least 10 feet (2 squares) on your mount and you can move up to double your mount’s speed directly toward the designated opponent. This applies no matter how big you or your mount is. A riding dog and an elephant both need 10 feet of movement to perform a charge. (73)
Emphasis mine. Another question reiterates the mounted charge language, and there, too, the FAQ doesn't mention that any of the querent's statements are erroneous. However, take the FAQ's ruling for what it's worth.
If the DM rules that a rider can charge independent his mount, the DM will have to adjudicate the effects of such feats as Leap Attack and Shock Trooper on a case-by-case basis. The rules don't seem designed to handle such cases and seem to expect—despite the FAQ's ruling—that the mount charges and the rider sits atop the mount and merely stabs, launches arrows, or casts spells instead of the rider somehow charging while still in the saddle.
1 A similar logic applies to the scout's special ability skirmish being unusable while mounted as per the Complete Adventurer errata.
2 No consequences are listed for failing this Ride skill check. Ask the DM. Or, y'know, don't and be surprised.
3 Which strikes me as deeply weird—the horse calmly trotting around and the furious, red-eyed knight viciously lancing folks from the saddle—, but whatever.