Martina Devlin explains why Sikhs should not be allowed to be guards:
It hinges on separation of Church and State. An Garda Siochana is an arm of the State and when its members are on duty it is inappropriate for them to display any memberships or predilections. The State is secular and its servants must be secular too — at least during those times when they button on their uniforms and represent the State.
The Garda website gives some info on the medals it hands out for bravery:
The medal is in the form of a Celtic cross, 44mm in diameter. There are five panels on the face. The inscription on the top panel are the words “The Scott Medal” and on the lower panel “For Valor” (note the American influence on the spelling). On the right and left are the eagle and shield of the U.S.A. and the harp and sunburst of Ireland, respectively. The centerpiece is from the Garda Crest with the intertwined letters G.S. – the initials of the words, Garda Síochána.
Thank God the state is secular.