https://lawshun.com/article/what-is-the-relationship-between... explains the complex relation between EU law and national law.

in a nutshell, EU law takes precedence over conflicting national laws in areas where the EU has competence.

While EU law is directly applicable or requires transposition into national law, member states retain autonomy in areas outside EU competence.

National courts are obligated to interpret domestic law in line with EU law.

National Constitutional Court/Supreme court, occasionally challenge EU law’s supremacy.

They can also just ignore it because the EU has no army, only economic retaliation is possible. Hungary did this for years.