from what i know "spearfishing" (that would include the polespear i guess) on scuba is illegal in protected/ sanctuary areas...
some resorts ban it all together (scuba or not)
there are some dive areas though that allow this... more often than not these are the off-the-beaten track areas and not the primary dive destinations (like anilao, pg, bora, malapascua, etc.)
personally? i frown upon it... hunting in general... especially on scuba... it doesn't give the fish a sporting chance... on apnea in a non-protected area - have fun - but i won't look at the pictures...
Jag