Security and command cannot use contraband or enable crew to outside of extreme emergenciess, like nukies. Uplinks are contraband, so are many of the items found in them. Other non-antag players do not have this restriction on the use of contraband so can operate uplinks.
While they are considered contraband, security and command may use or allow the use of syndicate radios or encryption keys to combat syndicate though deception, or communications interception/disruption, even in non-emergency situations. Security and command may not however use a syndicate uplink to purchase syndicate radios, or encryption keys.
The use of contraband generally allows others to treat someone as a confirmed antagonists and a dangerous threat. Non-antagonists who use contraband are still subject to all rules including self antagging and escalation. A non-antagonist in a blood red with an esword must still escalate conflicts in the same way as if they had no contraband, but others may choose to see them as a dangerous threat and immediately escalate to lethal force. While the non-antag with contraband would be allow to defend themselves in this situation, they’d still be responsible for getting medical attention for anyone that they crit, would not be allowed to attack security to “defend” themselves from an arrest, and attempting to bait people to attack them so that they can kill them would likely be considered self antagging.