Please Contact
this department for more information.
Gibraltar is part of the European as a UK dependent territory ( One of the only exception). The Surinder Singh principle applies to Gibraltar. As a UK national who has exercised his right of free movement by working in another memberstate, i.e Spain, you have an enforceable community right to enter Gibraltar with your wife, and if the authorities think your wife requires a visa, it would be issued to her their on production of proof of your nationality ( Your Irish or British Passport) and your marriage Certificate.
Alternatively you could show your Irish passport and enter as an Irish national. Either way, i think she will qualify.
Please note that if you enter there as a British national who has exercised free movement rights in another member state, you may need to provide the authorities with proof that you have been working or self-employed during the time you lived in Spain.