"the law is the law!"

You often hear the appeal to law fallacy being used in the imigration debate especially. You will hear
"If you immigrate come here LEGALLY"
"I know they are not violent, but they are criminals because they broke the law"

I assume that the pro borders crowd thinks having the central planning of human movement is okay, and they think it is necessary, so why do they claim borders should be enforced because of the law ( the literal term for the law is the threats on paper btw ).
It is often brought up that slavery was "the law" and they were completely wrong back then on what the law should be, but people disobeyed the law with a sense of common sense ethics the rest of the country lacked.

Slavery has been used to show why laws are okay to break sometimes, but People often reply to that with "how dare you compare the two!" (the person saying that statement is often someone that is being shown that there "it's the law!" defense can be used for terrible things when they priorly used that defense)

One thing most people do not comprehend is the difference between comparing and equating, equating slavery and border enforcement would be extreme.

But, through comparing we can see that the appeal to law doesn't justify said policy if it is shown to be immoral.

To anyone on the right that still defends "it is the law" argument, I will ask you this.

Are the gun control laws in Europe wrong or right?

Is Sharia law wrong or right?

With gun control for example the right uses "the 2nd amendment is the law so gun control is wrong" (I am very pro gun everybody don't worry)

I really don't understand why the appeal to law fallacy needs to be made here, they believe that gun ownership is a moral right and that gun control wouldn't help.

I seem to be picking on the right but I really do not see the left using the appeal to law fallacy, (I do have my disagreements with the left though)

There are those who say that if we all got to disobey laws we thought were unjust, wouldn't there be chaos? I'll link this video to them. "Fearing your own humanity by Larken Rose'

Video version