expression
dual system; double standard
Refers to a system or arrangement where two different standards, rules, or structures coexist, often with a critical nuance of inconsistency or unfairness.
その会社は社員と契約社員で二本建ての給与体系を取っている。
That company has a dual salary system for regular employees and contract workers.
彼の言動には二本建ての基準があるように思える。
His words and actions seem to have a double standard.