A more thorough explanation:

A collusive action is when two parties pretend to be adversaries in a legal case, but they actually agree on the outcome they want. They do this to get a specific answer to a legal question or to set a favorable precedent for future cases.

For example, in the 1943 Supreme Court case of U.S. v. Johnson, the plaintiff was not really involved in the case. They were represented by a lawyer, but they never showed up in court or had any say in the outcome. The court decided that this was a collusive action and dismissed the case without making a decision.

Another example of a collusive action could be two companies agreeing to a settlement in a lawsuit, even though they both know that the lawsuit has no merit. They do this to avoid the cost and time of a trial and to set a precedent for future cases.

Collusive actions are not allowed in the legal system because they undermine the fairness and integrity of the process. Judges and lawyers are supposed to make decisions based on the facts and the law, not on what two parties agree to behind closed doors.