GST has brought about a fundamental change in the Constitutional landscape, particularly Part XI of the Constitution which deals with the legislative relations between the Union and the States, has been almost rewritten. 

Earlier, there were three Lists in the Seventh Schedule, namely Union List, State List and the Concurrent List. In all the three Lists there were exclusivity between Parliament and the State Legislatures insofar as legislative actions were concerned. 

However there is a change, the change is so massive that there is an entirely reverse concept which has been brought about, instead of exclusivity there is concurrent decision making. Let me explain in detail, as to how there is a shift from exclusivity to concurrent decision making insofar as legislative institutions are concerned. 

Earlier, List 1 were subjects which were exclusive to Parliament, List 2 were subjects which are exclusive to States. List 3 is a Concurrent List which can be enacted upon by both the Centre and the States 

but there were certain rules namely doctrine of repugnancy, etc which will ensure that at any given point of time there is either the Union or the State law which will operate, which basically meant that there is only one law on a particular legislative subject. This has changed fundamentally. 

There is no subject introduced in either of the three Lists for GST. 

On the contrary, a new legislative subject has been created outside the three Lists. Article 246-A has been inserted in the Constitution which is the sole repository of GST. It provides that both the Centre and the States, namely the Union Parliament and the State Legislature can enact laws on the subject of GST. 

Therefore, Article 246-A is a standalone legislative subject as compared to legislative subjects generally being enumerated in Lists 1, 2 or 3. I am not saying this is unprecedented because there is Article 105, there is Article 194 which provides for enactment of law relating to parliamentary privileges and these are not under one of the three Lists. However, there is still a substantial change. The change is on account of the fact that Article 246-A relates to the law being made by the Parliament or the State Legislature, but upon the recommendations of the GST Council, which is a major and substantive change. 

The change being major because earlier the Parliament and the State Legislatures were exclusive, now they need to factor in the recommendations of another Constitutional Institution. Let me give you another example of this massive change. Earlier, the laws were made upon subjects which are enumerated under either of the three Lists. Now, a number of subjects have been removed from List 1 and List 2. 

For eg. the Union, cannot legislate upon excise duty insofar as almost all the goods except petroleum and tobacco is concerned. 

The States, they cannot levy luxury tax, they cannot levy entry tax, they cannot levy advertisement tax. They have been denuded of the powers to impose such taxes. All these taxes have been subsumed in a larger whole. That larger whole is collectively represented by GST, which is described as any tax on supply of goods or services. 

Therefore, there is a huge change because a number of legislative subjects have been omitted from exclusive powers of Parliament and State Legislature and these have to be enacted upon concurrently by both the Parliament and State Legislature and that too upon the recommendations of GST Council.