There’s been a lot of cheering today for the news that Massachusetts governor Deval Patrick plans to direct public colleges in the state to allow undocumented students to pay in-state tuition, but a peek at the fine print shows that the policy shift isn’t anywhere near what it could be.

The policy covers undocumented Massachusetts residents eligible for temporary immunity from deportation under the Obama administration’s new DREAM-Act-like policy, but there’s a catch. Actually two.

First, in order to qualify for in-state tuition, you have to have made your way through the Deferred Action for Childhood Arrivals (DACA) hoops and been granted the reprieve from deportation it provides. That means that if you’ve got qualms about coming forward, or you’re having trouble proving eligibility, or are stuck in the bureaucracy for some other reason, you’re out of luck.

Second, and more importantly, the program only covers DACA-eligible students. So if you’re over thirty, you don’t qualify — even if you’ve lived in Massachusetts for twenty years. If you came to the US after your 18th birthday, or you’ve got the wrong kind of criminal record, or you don’t have (or can’t prove) the uninterrupted presence in the country that DACA requires, you’ll continue be treated as an out-of-state student for tuition purposes.

And it’s important to note that there’s no reason for Massachusetts to be limiting in-state tuition this way. A number of other states have taken the more reasonable approach of applying residency rules to all students equally, no matter what their immigration status. Just this month, in fact, Maryland took that step by statewide referendum.

If you’ve been in state long enough to obtain residency, you’ve been a state resident long enough to get in-state tuition. That’s a simple, straightforward principle, and it should be the one that pertains in Massachusetts.

It’s a shame Deval Patrick doesn’t see it that way.