Moving the goalposts

Moving the goalposts or shifting the goalposts is an idiom which means changing the terms of a debate or a conflict after it has started.
The phrase describes changing the target or goal of a process. In a dispute or a competition, the idiom explains what one side does in order to gain advantage.
History.
This phrase comes from sports that use s, such as football.
In 1978, the "Washington Post" published the phrase, quoting the CEO of American Airlines who said, "'They keep moving the goal posts." In Britain, the earliest known published use was in 1987.
Logical fallacy.
The idiom identifies a kind of logical fallacy. In an argument, when evidence is presented in response to a specific claim, it is "moving the goalposts" when some other evidence is demanded instead. Idioms are a common stumbling block for learners of a language.
In other words, after an attempt has been made to score a goal, the goalposts are moved to exclude the attempt. The problem with changing the rules of the game is that the meaning of the result is changed too. It counts for less.
Bullying.
The tactics of bullying behaviour include moving the goalposts. This means setting objectives which subtly change in ways that cannot be reached. In workplace bullying, shifting the goalposts is a conventional tactic.