The UCMJ is enacted under Congressional powers, therefore not an Executive power. Meaning it’s power flows from Article I. Further, it does not somehow supersed

The UCMJ is enacted under Congressional powers, therefore not an Executive power. Meaning it’s power flows from Article I. Further, it does not somehow supersede the Supremacy Clause of Article VI, meaning it must still operate within the framework of the Constitution. The USMJ limits some rights but also expands others. For example, a “jury of your peers” can more accurately reflect the accused, you receive Miranda rights earlier, you can request summary judgment for criminal matters, etc. On the flip side, free speech is more constrained due to the societal need for an impartial military, and this has been upheld by the Supreme Court on multiple occasions.