West Bengal Chief Minister Mamata Banerjee on Monday termed as "unconstitutional" the Central government's amended rule forbidding cattle trade for slaughter and said the decision would be challenged legally by her government."This is a destructive attitude to federal structure, unnecessary bulldozing, encroaching and interference to federal structure," she said."The law is very clear. According to the Article 246 of Indian Constitution, the legislature of any state has exclusive power to make laws with respect to any of the matter enumerated in Seventh Schedule. The law is clear, still the decision is being forced down our throats. We are not accepting that. We will challenge it legally and constitutionally for interference in state power."This is a deliberate attempt to encroach the state power. This is absolutely unconstitutional, unethical and undemocratic," said Banerjee, also the Trinamool Congress supremo.She said that the Union Environment Ministry should have consulted the states before taking the decision.