in (one's) pocket
Under one's control or influence, especially in an underhanded or unethical way, such as by bribery or extortion. It's pretty obvious that our national legislators are all in corporate bigwigs' pockets! I hear that the boss has half the police force in his pocket.
in someone's pocket
If you are in someone's pocket, they control you and you do everything that they tell you. Surely there was a judge somewhere who wasn't in Jason's pocket. The Labour party suffered badly from claims that it was in the pockets of the unions.
in someone's pocket
dependent on someone financially and therefore under their influence.