We expected Gov. Mitt Romney to be criticized by immigrant-rights advocates for his decision to authorize 30 state troopers to detain and arrest illegal aliens, but they aren’t finding fault for the right reasons.

The real problem with Romney’s measure is that there is no backup from the federal government. Once arrested, where are illegal immigrants going to be held? Where is the detention center? Who will pay to deport them?

According to the deal with U.S. Immigration and Customs Enforcement, an initial group of 30 troopers will receive five weeks of specialized training next year, paid by the federal government. After training, the troopers will receive a certification allowing them to question, detain and arrest suspected illegals, charge them with a violation of immigration law and place them in removal proceedings.

But there is no place for the illegal immigrants to be held and no federal funds provided to pay for deportation. Will Massachusetts taxpayers be expected to pick up the tab?

It is estimated that there are 200,000 illegal immigrants in Massachusetts and the vast majority are otherwise law-abiding residents. But some are not. Some illegal immigrants are here for nefarious purposes or fall into unlawful habits.

However, we don’t believe troopers should go looking for trouble without more support from the federal government.

We believe Romney is correct in saying illegal actions cannot be tolerated, but by not having increased federal assistance tied to this measure and with Gov.-elect Deval Patrick already investigating ways to nullify the deal, there is little that will actually be accomplished.