A sovereign nation is one which makes it's own laws.
Most people in the United Kingdom,including most politicians,regard their country as a sovereign nation.
Most believe they are ruled by the laws made by the parliament which they elect.
Unfortunately,that is not the case.
This is made clear in the Final Act of the Intergovernmental Conference on the Lisbon Treaty:
"Declaration concerning primacy
The Conference recalls that, in accordance with well settled case law of the Court of Justice of the European Union,the Treaties and the law adopted by the Union on the basis of the Treaties have primacy over the law of Member States,under the conditions laid down by the said case law.
The Conference has also decided to attach as an Annex to this Final Act the Opinion of the Council Legal Service on the primacy of EC law as set out in 11197/07 (JUR 260):
"Opinion of the Council Legal Service of 22 June 2007
It results from the case-law of the Court of Justice that primacy of EC law is a cornerstone principle of Community law.
According to the Court, this principle is inherent to the specific nature of the European Community.
At the time of the first judgment of this established case law (Costa/ENEL,15 July 1964, Case 6/641*) there was no mention of primacy in the treaty.
It is still the case today.
The fact that the principle of primacy will not be included in the future treaty shall not in any way change the existence of the principle and the existing case-law of the Court of Justice."
*“It follows… that the law stemming from the treaty,an independent source of law,could not,because of its special and original nature,be overridden by domestic legal provisions,however framed,without being deprived of its character as Community law and without the legal basis of the Community itself being called into question.”