Well the players and bookies have been charged under India Penal code 420 whose description is below. The offense is criminal and punishable upto 7 years in prison plus fine.
420. Cheating and dishonestly inducing delivery of property
Whoever cheats and thereby dishonestly induces the person deceived to deliver any property to any person, or to make, alter or destroy the whole or any part of a valuable security, or anything which is signed or sealed, and which is capable of being converted into a valuable security, shall be punished with imprisonment of either description for a term which may extend to seven years, and shall also be liable to fine.
Source Bare Act IPC
There is no separate code for fixing matches yet, because in the past the money offered for match fixing or spot fixing was too low and most players won't risk their career for such money, so the punishment of banning the player from playing cricket was enough. But these days, the money offered is enormous and the players don't seem to mind being banned for such big money. So new laws are needed now, but weren't needed in the past. Can you answer my question pls?