Fundamental Rights
Parliament may, by law, determine to what extent any of the rights conferred by this Part shall, in their application to - (a) the members of the Armed Forces; or (b) the members of the Forces charged with the maintenance of public order; or (c) persons employed in any bureau or other organisation established by the State for purposes of intelligence or counter intelligence; or (d) persons employed in connection with the telecommunication systems set up for such Forces, bureau, or organisation - be restricted or abrogated so as to ensure the proper discharge of their duties and the maintenance of discipline among them.
Parliament can pass laws that limit how Fundamental Rights apply to members of the armed forces, paramilitary/police forces, intelligence agencies, and related communication staff - but only to the extent needed to maintain discipline and ensure they can properly do their duties. This is why, for example, certain free-speech or association rights are more restricted for serving soldiers than for ordinary citizens.
Restrictions on armed forces personnel joining trade unions or publicly criticising military policy are permitted under Article 33-specific laws like the Army Act - a restriction that would be unconstitutional for an ordinary citizen can be valid here because Article 33 specifically allows it for this narrow group.