It is letting folks know you may be asserting it after the fact and you aren't waiving your right. What you are doing is establishing that the search isn't voluntary and that your cooperation is not consent.
I don't know how different circuits would look at it. My understanding is that this would not be effective in the 5th and 11th circuits since they hold that you consent to searches when you get in line and you can't revoke that consent. But other circuits haven't gone that far. That means that if they want to hold the search as lawful, they have to establish that it is a valid administrative search, and that consent is not required.
It would be clearer if "you may" was replaced by "I am aware you may" clarifying that this is not permission but a statement of possibilities.
I don't know how different circuits would look at it. My understanding is that this would not be effective in the 5th and 11th circuits since they hold that you consent to searches when you get in line and you can't revoke that consent. But other circuits haven't gone that far. That means that if they want to hold the search as lawful, they have to establish that it is a valid administrative search, and that consent is not required.
It would be clearer if "you may" was replaced by "I am aware you may" clarifying that this is not permission but a statement of possibilities.