old guard 
noun
The original or long-standing members of a group, regarded as unwilling to accept change or new ideas: the ageing right-wing old guard...
- He was too easily swayed by others and too anxious to be accepted by the old guard of the Senate.
- This week, though, the old guard will aim to re-impose the established order.
- You've got a built-in bureaucracy - people will fight tooth and nail to keep their positions - and there are old guards in the ruling party.