The March 14 directive, signed by Attorney General Pam Bondi, uses an obscure 18th-century law — the Alien Enemies Act of 1798 — to give law enforcement nationwide the power to bypass basic constitutional protections.
According to the memo, agents can break into a home if getting a warrant is “impracticable,” and they don’t need a judge’s approval. Instead, immigration officers can sign their own administrative warrants. The bar for action is low — a “reasonable belief” that someone might be part of a Venezuelan gang is enough.
That's true pretty much everywhere. Shooting someone in the back will almost always get you charged, unless you're a cop.
Generally speaking--and I'm not a lawyer, I'm not your lawyer, and you should ask a criminal defense attorney in your state for specifics--you can use force, including lethal force, to protect your life if you have reasonable fear for your life or safety. Generally speaking, if someone is running away from you, they're no longer a direct threat, and therefore you can't use force. Similarly, if you are in a reasonable fear for your life, and you shoot someone, you can not kick them while they're bleeding on the ground.
I believe all states have some form of Castle Doctrine. Some states have a duty to retreat if you aren't in your home/car, e.g., you have to attempt to escape first. Some states require you to use proportionate force; if they have a baseball bat, you may not be allowed to use a firearm. Know the laws specific to your state.