"Our office is not able to literally ignore that the local mandate law does require contemporaneous funding be appropriated," DiZoglio said.

It's yet another hurdle for the MBTA Communities Act, which mandates cities and towns served by the T make it easier to build multifamily housing within their borders.

The state auditor determined last week that the MBTA Communities Act was an "unfunded mandate," giving towns that don't want to comply with the law a potential avenue to challenging it.