[Leaning Right]

Here's something interesting about the National Guard I found on Wikipedia. Doesn't this imply that the President can issue orders to the Guard only if Congress approves?

The National Defense Authorization Act 2008

Repeals provisions in section 1076 but still enables the President to call up the National Guard of the United States for active federal military service during Congressionally sanctioned national emergency or war.

[MaxMax]

Doesn't this imply that the President can issue orders to the Guard only if Congress approves?

An act of Congress is one method for authorization but the Constitution also
allows the President to call up any American forces in order for him to perform
his Duty compelled by his oath as POTUS to protect our country from attack,
or in this case, invasion.

The president can order the border closed at any time without any approval
under most circumstances, health and welfare being one, invasion another.
There are more but they're not relevant to what's happening.