"The Golan was used to fire down on Israeli farms until they finally took it from Syria,"
Israel, iwith its well trained army and all the military strength at its disposal is more than capable of defending itself without persecuting Third world Arabs

"With its well trained army and all the military strength at its disposal" Israel very nearly lost that war.
There is no defence against dug in artillery firing down from high ground except to take that ground, which Israel finally achieved at great cost.
It was not illegal because Syria had declared war and because shelling farmers is a war crime. Syria is still in a state of war with Israel.