My players fought a mage who was going to drop Leather Repulsion Armor, so I had the mage use the power during the fight.
Repulsion Armor's power reads:
Power(Daily): Minor Action. Whenever an enemy moves into an adjacent square, you can push that enemy 1 square as an immediate reaction. This power lasts until the end of the encounter.
One of the players moved to the mage to make a melee attack, so I pushed them 1 as an immediate reaction. They hadn't moved their full speed to get there, so they just went ahead and moved one more square to be adjacent to the mage again.
I wasn't sure how to react to that, on one hand their interpretation made sense, but since the power is an immediate reaction, I was considering it to occur after the player finished their movement. In other words, their action was over so they couldn't use it to move anymore, even though they didn't use all their movement.
I couldn't decide, so I did the default and let them do it, but this pretty much ruined the armor and the mage for the whole fight. Now one of my players is wearing the armor, and I need to decide how to treat it in the future. If enemies can still just walk right up to them, then it's kind of pointless.
How does this power work?