Is this legal to change the paid time off around the holidays after vacation days were approved?

My employer had a holiday policy that gave the following days paid - 12/23, 12/26 and 1/2. I requested three days paid vacation 12/27-12/29 and a floating holiday 12/30. We only have 5 vacation days a year of which are granted only after 6 months of continuous work. After my vacation was approved, accepted, and calendared, they changed the policy because they didn't like that I leveraged the policy to get 11 days off. Now, they are saying I will not get paid time off for 12/23, 12/26, and 1/2 if I use my scheduled vacation days. They want to change the policy after I had a scheduled vacation. They will not allow me to work 12/23 because the office will be closed. So I either will be forced to work the days I requested off 12/27-12/30 to get the given days, or unpaid days off.