He hasn't before even though he has made this threat many times. I don't even think he is that stupid to shut it completely down. It is the busiest border in the world, with more than a million people legally crossing each way every single day. It would destroy business on both sides of the border and hurt the economy. I don't think people really understand the amount of legal trade that goes on at the border. They just think of big industry like Boeing or Ford, but millions rely on the small level trade both ways. Not only that, if it creates an economic vacuum, you'll actually see illegal immigration increasing.
This is akin to the gun ban arguments. If you ban people from owning guns, you won't stop criminals from owning them, only law abiding citizens. The criminals will still have their guns and scoff and the demand they turn them in.
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A strong demurral.
When one elevates/chooses principal over principle, he sends a clear message:
* that he can be bought for a price and
* that he is of low and little character.
So too, Nations survive and thrive by adherence to enduring principles, otherwise
they soon enter the dustbin of history. The Greeks fostered the virtue of Prudence;
measuring decisions taken/not taken in the now against their consequences in future.
Not enforcing our Sovereign Rights as a Nation and a People is a message to our
enemies that we are unserious about our founding principles.
The consequences of this will be grave.