Lucario vs shield -- aerial + force palm = free damage?

[Mean Green]

I can't seem to get it quick enough. But I'm wondering, is that an unpunishable combination?

 

[Ike Tyson]

I have success when the opponent blocking on a platform or when I rise Fair->B from the ledge.

 

[Mean Green]

Well that's good. But I really meant like if you're using a desperate force palm. For example, you're landing into the opponent's frontside using n-air or f-air, and it hits their shield, then you side-B. If they tried to shield grab you then, would you get punished? Or is it like the first person to grab, gets the grab?