judicial review is a check on the legality of use of executive power as granted by parliament, not on parliament's ability to legislate if parliament legislate

judicial review is a check on the legality of use of executive power as granted by parliament, not on parliament's ability to legislate if parliament legislated to grant the government the ability to do whatever it wanted in regards to HS2 then there would be nothing for judicial review to... review the government can also override local authorities for planning decisions for e.g. projects of national significance