The Intersection of Dormant Commerce Clause & Supremacy Clause

I am going mad, guys! Can someone help me out with this? So, we're discussing the case of Gebser v. Lago Vista (1994), where the Supreme Court found a violation of Title IX of the Education Amendments of 1972. Now, my problem lies in understanding the interplay between the Dormant Commerce Clause and the Supremacy Clause. If a state law violates the Dormant Commerce Clause, is it then automatically preempted by the federal law under the Supremacy Clause, or does it still have an effect despite being unconstitutional? In other words, can I still look at the state law as a 'law', even if it's being ignored by the federal government due to the Supremacy Clause? Can someone throw some light on this, please?