Legitimate executive orders communicate from the chief executive to members of the executive branch issues of policy - how to enforce the law, how to comply with the law, and how to comply and enforce the Constitution. A sure way to tell if an executive order is illegitimate is if it defines some act that citizens are required to do or prohibited from doing under threat of punishment.
No one should comply with an executive order directed at citizens and no law enforcement officer who wants to honor his or her oath should have anything to do with attempting to enforce it.
Here is the Texas separation of powers constitutional provision:
ARTICLE 2. THE POWERS OF GOVERNMENT
Sec. 1. SEPARATION OF POWERS OF GOVERNMENT AMONG THREE DEPARTMENTS. The powers of the Government of the State of Texas shall be divided into three distinct departments, each of which shall be confided to a separate body of magistracy, to wit: Those which are Legislative to one; those which are Executive to another, and those which are Judicial to another; and no person, or collection of persons, being of one of these departments, shall exercise any power properly attached to either of the others, except in the instances herein expressly permitted.