Moving the goalposts (or shifting the goalposts) is a metaphor, derived from goal-based sports, that means to change the rule or criterion (goal) of a process or competition while it is still in progress, in such a way that the new goal offers one side an advantage or disadvantage.

(“Moving the Goalposts” 2022)

References

“Moving the Goalposts.” 2022. Wikipedia, June. https://en.wikipedia.org/w/index.php?title=Moving_the_goalposts&oldid=1092754084.