Way back in 2010, voting rights were granted to NRIs in India. However it is required for NRIs to physically be present in India to cast their votes. This is practically impossible and hence the so called voting rights to NRIs is a myth.
Presently e-voting has been resorted to under Company’s act and ITACT2000/8 has provided a legal base for e-voting long time back. In fact the EVMs itself is a kind of e-voting mechanism where the voter’s choice is captured in the form of an electronic document, retained and processed as electronic documents, all under the provisions of ITA 2000/8.
It is therefore not logical for ECI to refuse digital signature based voting for NRIs. Unless ECI is facing opposition from the ruling Congress party for such a move under the fear that it may benefit the BJP, there is no reason why this system should not be introduced in the next Loksabha elections.
Probably ECI can set up a centralized digitally signed e-voting system and make it available to all voters whether in India or abroad to cast their votes through a valid digital signature issued by an Indian licensed Certifying authority.
In the least, this facility can be offered to the NRIs who have no other option.