First of all, Israel left Gaza in 2005. They no longer govern it. In addition, they have been allowing huge amounts of cash flowing into the region and they are even unable to impose a full blockade considering the border with Egypt. If Palestinians are so peace-loving individuals, why the relations with Egpyt are far from ideal, too? Hence why it is mostly Hamas responsible for the situation in Gaza.
So yes, a response is fully excepted if members of a different state (that by the way wants to exterminate Israel) illegally cross the border.