Republican candidates for president have often taken a get-tough approach on deterring illegal immigration, but they usually focus on the border with Mexico. Walker was asked Sunday morning on NBC’s “Meet the Press” whether he wanted to build a wall on the northern border, too. Walker said some people in New Hampshire have asked the campaign about the topic.

“They raised some very legitimate concerns, including some law enforcement folks that brought that up to me at one of our town hall meetings about a week and a half ago. So that is a legitimate issue for us to look at,” Walker said.

The U.S.-Canada boundary is the longest international border in the world at 5,525 miles long.