Because “unreasonable” is the qualifier, and searches at the border have (since the 4th Amendment was written) been considered per se reasonable as an exercise of a sovereign nation’s powers to create and maintain a border.

Yes, I understand the qualifier is what gives the government legal wiggle room, but I don't understand why it's reasonable that you lose constitutional rights the second you cross a border and come back. Constitutional rights should travel with you.

And by "border" you mean the actual border + 100 miles inland, right?

https://www.aclu.org/know-your-rights-governments-100-mile-b...

No. The 100 mile thing just means that you don't have to be exactly at the border and that if the search area is moved a bit for geographic convenience that's fine. You still have to have recently crossed a border to be searched.

There is no reason to be alarmist.

Border Patrol also stops people in the 100 mile zone to inquire about their immigration status. You can be detained or searched in this way regardless of anything having to do with a border crossing.

Big difference between "not exactly at the border" and 100 miles away from it.

Also not very helpful that the search is illegal if you haven't crossed a border and have to get relief in court against a federal agency.

No one is being searched by border patrol who hasn't actually crossed a border. There's no need for anyone to get relief.

There is no reason to be alarmist.

>who hasn't actually crossed a border

You mean like ever in their lifes? If not, some people might disagree with you:

http://www.concordmonitor.com/New-Hampshire-interstate-borde...

Or you can claim that border patrol tracked these people for 75 miles and then held them up at the road block.