5. Implementing the constitutional mandate for decentralization and local autonomy, Congress enacted Republic Act No. 7160, otherwise known as the Local Government Code (LGC), in order to guarantee the fiscal autonomy of the LGUs by specifically providing that: "local government units shall have a share in the national internal revenue taxes based on the collection of the third fiscal year preceding the current fiscal year as follows: x x x (c) on the third year and thereafter, forty percent (40%)." According to the implementing rules and regulations of the LGC, the IRA is determined on the basis of the actual collections of the national internal revenue taxes (NIRTs) as certified by the Bureau of Internal Revenue (BIR). Discuss whether the foregoing is constitutional or not