The law seeks to demote him because his father and ancestors were from Uttar Pradesh, though he himself was born in Chapra district of Bihar, where his father worked as an railway employee for 25 years.

Maurya and others like him have approached the apex court after losing their first round legal battle in the Patna High Court, which dismissed their lawsuit against the law last month, seen as the judiciary's general reluctance to invalidate government laws to avoid criticism of stepping into the legislature's domain.

When the lawsuits filed by Maurya and others came up for hearing last Friday, a bench of Chief Justice K.G. Balakrishnan, himself a Dalit, ordered the Bihar government against tinkering with its Dalit employees' ranks until after the disposal of their suits challenging the constitutionality of the law.

The bench, which also included Justice P. Sathasivam, asked the Bihar government to file its reply to the suit.

The Bihar government amended the law in 2003 on quota for Dalits after noticing in 1996 that some Dalit communities of the state, such as Chamar, do not figure in the Scheduled Castes lists of states like Uttar Pradesh and Madhya Pradesh, and accordingly get no quota benefits there in state employment or education, said Maurya's lawsuit.

This in turn implied that states like Uttar Pradesh and Madhya Pradesh do not accord quota benefits to the people of Bihar from the Chamar and some other communities, despite their Scheduled Caste and Dalit status in their native state. Accordingly, the Bihar government amended its law to provide that people of other states who do not figure in the Scheduled Caste lists in their native states will not get any reservation benefits in Bihar either.

The Bihar government amended its Dalit quota law with retrospective effect from 1996 - when it had first noticed the mismatch in quota benefits in different states and had issued an executive order to deny quota benefits to people of other states.

But the 1996 order, devoid of the force of law, proved futile in stopping Dalits from other states claiming reservation benefits in promotion. According to Maurya's lawsuit, the 2003 amendment sought to divest people like him of promotions they had got after 1996 or earlier.

In the lawsuits filed on behalf of Maurya and others, their counsel Sridhar Potaraju has pointed out that the 2003 amendment negates the constitutional provisions under Article 16(2), which bars any discrimination on grounds of race, religion, sex or place of birth in state employment.