The phrase "to change the rules" means to make alterations or adjustments to the established guidelines or regulations that govern a particular situation or system. Full definition
Although it does not change the rules of the road for already completed divorces, it will significantly impact future divorces. (apfmnet.org)
As you know, lenders have changed their lending criteria dramatically and credit bureaus have changed their rules for how they score you and your customers, tenants and buyers. (atlantareia.com)
This is a simple case of changing the rules in the middle of a game when you think it's too hard. (wattsupwiththat.com)