BOISE — Idaho college students face some of the toughest restrictions in the nation when trying to register to vote at their college addresses, according to a national study.

Idaho admonishes students they can register at their college address only if they plan to stay in the state permanently, the Spokesman-Review reported. Officials at New York University Law School's Brennan Center for Justice said this interpretation of the law, similar to practices in Tennessee, could be unconstitutional.

Often seen as only marginally politically active, college students could make a difference in close elections if they go to the polls. But their impact will remain muted if they don't vote due to rules that some deem overly restrictive, Brennan Center officials said.

"Many students are in a situation where they don't know where they're going after school — for all intents and purposes, this is their only residence," said Wendy Weiser, director of voting rights and elections at the Brennan Center. "To say that you actually have to have a definite plan to remain in Idaho means that all the people who haven't determined what their future plans are, are for all intents and purposes disenfranchised."

Idaho Secretary of State Ben Ysursa said Idaho's laws governing residency for voting purposes don't differentiate between students and non-students. According to his office's Web site, students should not be registering and voting in their college locales simply because they failed to register in their true domicile.

"There are limits, and we stand by what we have put out in writing on how you define residency," Ysursa said, adding he's received few complaints. "Is there 100 percent clarity on residency law? No. There are factors that you have to figure in, but there are factors for everyone, not just for students."

His Web site warns that voters who abuse the law could face criminal penalties. The Brennan Center's Weiser said the threat is intimidating.

"This is something that we're actually seeing in other parts of the country as well, when there are efforts to dissuade students from registering and voting in their school communities," she said.

Though Idaho's voter-registration law is nearly identical to neighboring Washington state's, the attorney general's office just across the border has offered the opinion that students can either register at their home address and get an absentee ballot, or they can register on their campus by using their campus address.

That's the common practice across most of the nation, after U.S. Supreme Court decisions in the 1970s upheld the rights of college students to be treated no differently from any other voters. In one race-related case, a mostly white Texas county required students at a mostly black state college to fill out questionnaires before registering.

This year, threats over voter registration have become an issue in Virginia when students at Virginia Tech were warned by a county registrar of elections that they could lose financial aid or ability to be claimed as dependents on their parents' tax returns if they registered to vote at their school addresses. The warnings were inaccurate.

Idaho did receive praise from the Brennan Center for allowing voters not registered in advance to register at the polls on the same day as the election.