If he does, he’s also violating Title 8 of Federal law, and his duty under his Constitutional oath to defend the US from foreign invasion.

Are you going to violate the Constitution and work for foreign invasion, Mr. Biden?

Any US President who does not defend the US Constitution is an illegal President.

https://www.breitbart.com/politics/2020/12/22/joe-biden-to-dismantle-trumps-legal-wall-inviting-central-americans-to-southern-border/