With so little context, GMS could be any number of things. For instance, if we are talking about policies, it could refer to the e-Government Metadata Standards
https://en.wikipedia.org/wiki/E-GMS

Or it could be a file extension

In any case, I would not translate the acronym itself. At best, you could put something like:
Type de document GMS (**traduction en français**) : politique/rêglement/directive.
(policy peut être traduit de différentes façons selon le contexte)