Very simple.
Anyone can draft a Bill with the justification of matter in the public interest (In the interest of People of India). Even a single citizen can draft it and can agitate to put up the same Before Parliament. Further it is up to the Parliament.
It says the democratic constitution of India. It is People’s State and it is not a State of the Government or it is also not the State of any Member of Parliament. Every citizen is the Master of the State if he/she initiate a matter in the interest of People of India subject to that the majority in Parliament accept the same.