If it was set in stone then there would never have been the need to have a panel of Judges vote on particular subjects or if they voted on a 'non-changing' document it would have to be 100% for or against and then the decision becomes unchangeable just like a Papal decree.
Im afraid they werent given this power but took it upon themselves. Once more they should at least have a two thirds majority just like the congress to change anything. If its 5 to 4 then the original ruling of the prior court should stand and the case thrown out of the supreme court. Sort of like a hung jury. You should need 6 voted to overturn something. This would put an end to judicial tyranny. You would never get 6 of them to agree on anything