Of course they can change the rules, did you pay them or sign a contract?
Why would their be a fine print? There is no contract!
CEX are giving away free LTC, celebrate it and stop crying about it
Of course they can change the rules, and of course "their" being no fine print or contract means they can decide to even start charging us LTC for the privilege of mining on their pool. However we can also dislike this kind of bait'n'switch in any way we prefer, so stop crying about it.