I think, parliament has power to alter supreme court decisions.
If you remember, supreme court declared that impeachment against Ex CJ Shirani Bandaranaike was unconstitutional. However parliament did not take it to its consideration.
Sorry it is wrong. Parliament cannot hear an appeal from SC decision. The final appeal is SC and matter ends there. There were few applications where it had gone wrong to Review with Full Bench , but so far such applications were rejected without considering merits. So in simple terms once SC decides the matter ends there. (there are few exceptions to this which I refrain due to complexity if one is interested can study LMSL divesture case where then CJ (S.N.Silva J) made glaring 'blunders' so some additional orders were made but this was done in the guise of 'clarification' of judgment . If you cant understand just forget that part. Even most lawyers will not know /understand this as there was no law to do such things. A research topic for aspiring academic ! (In SL it is very rare to find such work of research and that is also one reason that courts deliberately make wrong decisions eg Recent injuction granted against a bank , not to pay money on LC which was clear and unconditional.
SC and Paliament, both do not interfere with their decisions . Parliament also has power to hear a case of violation their privileges and can even punish! No appeal from such decision .
But parliament can pass a law that can nullify the effect of a judgment. This happens prospectively not retrospectively. So normally there will not be an effect to that case or parties. But in future the effect of judgment will not be valid. (Complex ?!)
eg Though there are lot of wrong judgments very rarely this happens the most recent being amendment brought regarding Gifts in REVOCATION OF IRREVOCABLE DEEDS OF GIFT ON THE GROUND OF GROSS INGRATITUDE ACT, No. 5 OF 2017 this was to correct a wrong decision, that created havoc in financial instructions who were not a party to that action. But unfortunately parties to wrong decision was not affected by this legislation! This happens due to heavy lobby , not by the parties to judgment but others who will also be affected by the said decision in future. So future application can be nullified. Hope you got it.
Ps
SC has no power regarding impeachment of CJ. What happened in this case was lawyers for ex CJ S.B filed a writ application challenging certain irregularities in the process of impeachment (eg charges, process followed etc) . Since Writ was filed in Court of Appeal and impeachment is a constitutional matter CA referred interpretation of a provision to SC. SC gave their deicsion regarding interpretation and send the case back to CA which granted writ quashing impechment process from the begining. But parliament did not heed to this decision and took a vote and ex-CJ was removed. This is legal as speaker is not bond to take court decisions.
In contrast if a Bill is referred to SC for determination of constitutionally as an urgent bill the parliament changes the bill accordingly, A Bill can also be challenged before passed in to law by parliament such decisions of SC followed by parliament before law is passed eg Port City Bill