In a long-running dispute, a third party had challenged the consent via judicial review in Belfast's High Court, with that challenge denied in October 2017.
That decision was then challenged in the Court of Appeal, which Galantas advised on Friday had failed, "thus the planning consent is confirmed".
Galantas said it was continuing with its planned raising at 5p or C8.6c per share, designed to raise up to £4 million (US$5 million), to bring Omagh into commercial production.
It had recently raised C$1.57 million (US$1.2 million) at 4.2p or C7.1 per share for underground development.
Mining entrepreneur Ross Beaty increased his stake during that raising to 17.9% of Galantas.
The company shipped its first gold and silver concentrate from Omagh in Northern Ireland's County Tyrone earlier this month.
The former openpit mine operation was suspended in 2013 pending consent for the underground development. Work on the decline at the base of the pit starting in early 2017 with Galantas saying it was advised its consents remained valid until judgement.
Galantas' Toronto-listed shares (TSXV: GAL) touched C14c on Friday, before closing up more than 18% to close at 13c, capitalising it close to $25 million.
In London, its AIM-listed shares (AIM: GAL) touched 8.695p intraday, closing up more than 14% to 7.15p putting its value at £12.02 million.