Emloyee transferred from Mexico by my employer, what if they lay me off?

[shooter]

They brought me to USA three years ago with a L1; currently I have my I-140 approved but waiting for the I-485, so I am still being partnered by my employer; in case they lay me off, do they must move me back to Mexico again? because I am transferred, do they must lay me off under USA laws / Mexico laws / both? PLEASE HELP please give details!