a closed shop

a closed shop

A field of business or competition in which only people adhering to certain criteria are allowed to join or participate. A reference to factories that only allowed people belonging to a particular union to work there. Despite the recent advances of gender and race equality, this industry remains a closed shop for wealthy white men. Up until relatively recently, journalism was a closed shop, open only to those with a very specific educational background. With the advent of the Internet, though, anyone can be, or at least call themselves, a journalist.
See also: closed, shop
Farlex Dictionary of Idioms.

a closed ˈshop

a factory, etc. where only people belonging to a certain union may work
See also: closed, shop
Farlex Partner Idioms Dictionary
See also:
  • be brought in from the cold
  • bring (someone) in from the cold
  • greatest of all time
  • splice (something) to (something else)
  • splice to
  • charts
  • compete in
  • compete in (something)
  • be not playing the game
  • challenge (someone) to (something)
References in periodicals archive
The latter not only insist on Premiership clubs being the only ones to run recognised youth academies,but operate such a closed shop that Rotherham, who were refused promotion to the Premiership 12 months ago,have only been grudgingly admitted the second time round,and even now will not receive as much cash as their club rivals.
Rugby Union: In Touch - MERSEY STARS SHINE ON NATIONAL STAGE