Ranbaxy''s marketing opportunity from this has been estimated by analysts at upwards of $200 million. Of this, they felt revenue from generic Nexium would top $160 million. In a petition filed at the District Court of Columbia last week that was reviewed by ET, Ranbaxy contended that the FDA had overstepped its jurisdiction by revoking approvals granted to the company years back. Dubbing the FDA''s decision as "arbitrary, capricious and contrary to law", Ranbaxy said "FDA has no power to correct an alleged ''mistake'' it made six years ago". The company didn''t respond to queries sent by ET as of press time. Earlier this month, FDA struck down its earlier approvals to Ranbaxy saying it had erred in granting them, given "compliance issues" related to the plant making the drugs. Ranbaxy had sought approval of the drugs made at its Paonta Sahib facility, which has been blacklisted by the US regulator since 2008 for lapses in prescribed manufacturing practices and other data flaws.