The petitioners challenged the Court to issue a writ of mandamus commanding the respondents, Land Transportation Franchising and Regulatory Board (LTFRB) and the Department of Transportation and Communications (DOTC), to require public utility vehicles to use compressed natural gas (CNG) as alternative fuel.

There were two main legal issues. First, whether the petitioners had standing to sue. Second, whether the writ of mandamus could be issued against the respondents.

Concerning the first issue, the Court recognised the petitioners’ standing to sue, taking into account the petitioners’ fundamental rights to clean air and the principle of the transcendental importance to the public.

However, as regard to the second issue, the Court determined that mandamus was available only to compel the doing of an act specifically enjoined by law as a duty. Since the petitioners were unable to establish that there was an indubitable legal duty on the respondents to order owners of public vehicles to use CNG, a grant of the writ of mandamus was not justified.