The Mullai Periyar dam controversy between Tamil Nadu and Kerala is threatening to develop into a legal battle. A clear indication to this effect was given today in the Tamil Nadu Assembly by Mr. Durai Murugan, PWD Minister, who said the State would explore legal measures to establish its right for storing water in Mullai Periyar dam up to 152 ft mark against the present 136 ft.The Minister was highly critical of Kerala's "adamant attitude" even though Tamil Nadu had complied with all its demands.