Then there is Article 1 Section 10, which allows any governor to protect his borders from invasion if the feds can’t or won’t.
Any border governor could ask for volunteers to build fencing along their border. Fences are not rocket science. A double fence that is continuously watched is very effective.
Right! A monitored double fence is the ultimate and cheap to build. A heck of a lot cheaper than allowing in uneducated illiterate illegal aliens. Monitoring by sensors and TV plus monitoring and armed response by the Border Patrol and US military