A SERVICE MAY , IN ORDER TO DO SO , TEMPORARILY PURSUE HIS ACTIVITY IN THE STATE WHERE THE SERVICE IS PROVIDED , UNDER THE SAME CONDITIONS AS ARE IMPOSED BY THAT STATE ON ITS OWN NATIONALS . AS THE COURT HAS REPEATEDLY EMPHASIZED , MOST RECENTLY IN ITS JUDGMENT OF 17 DECEMBER 1981 IN CASE 279/80 WEBB ( 1981 ) ECR 3305 , THOSE PROVISIONS ENTAIL THE ABOLITION OF ALL DISCRIMINATION AGAINST A PERSON PROVIDING A SERVICE ON THE GROUNDS OF HIS NATIONALITY OR THE FACT THAT HE IS ESTABLISHED IN A MEMBER STATE OTHER THAN THAT IN WHICH THE SERVICE MUST BE PROVIDED . THUS THEY PROHIBIT NOT ONLY OVERT DISCRIMINATION BASED ON THE NATIONALITY OF THE PERSON PROVIDING A SERVICE BUT ALSO ALL FORMS OF COVERT DISCRIMINATION WHICH , ALTHOUGH BASED ON CRITERIA WHICH APPEAR TO BE NEUTRAL , IN PRACTICE LEAD TO THE SAME RESULT .
9 SUCH IS THE CASE WITH NATIONAL LEGISLATION OF THE KIND IN QUESTION WHEN THE OBLIGATION TO PAY THE EMPLOYER ' S SHARE OF SOCIAL SECURITY CONTRIBUTIONS IMPOSED ON PERSONS PROVIDING SERVICES WITHIN THE NATIONAL TERRITORY IS EXTENDED TO EMPLOYERS ESTABLISHED IN ANOTHER MEMBER STATE WHO ARE ALREADY LIABLE UNDER THE LEGISLATION OF THAT STATE FOR SIMILAR CONTRIBUTIONS IN RESPECT OF THE SAME WORKERS AND THE SAME PERIODS OF EMPLOYMENT . IN SUCH A CASE THE LEGISLATION OF THE STATE IN WHICH THE SERVICE IS PROVIDED PROVES IN ECONOMIC TERMS TO BE MORE ONEROUS FOR EMPLOYERS ESTABLISHED IN ANOTHER MEMBER STATE , WHO IN FACT HAVE TO BEAR A HEAVIER BURDEN THAN THOSE ESTABLISHED WITHIN THE NATIONAL TERRITORY .
10 FURTHERMORE , LEGISLATION WHICH REQUIRES EMPLOYERS TO PAY IN RESPECT OF THEIR WORKERS SOCIAL SECURITY CONTRIBUTIONS NOT RELATED TO ANY SOCIAL SECURITY BENEFIT FOR THOSE WORKERS , WHO ARE MOREOVER EXEMPT FROM INSURANCE IN THE MEMBER STATE IN WHICH THE SERVICE IS PROVIDED AND REMAIN COMPULSORILY AFFILIATED , FOR THE DURATION OF THE WORK CARRIED OUT , TO THE SOCIAL SECURITY SCHEME OF THE MEMBER STATE IN WHICH THEIR EMPLOYER IS ESTABLISHED , MAY NOT REASONABLY BE CONSIDERED JUSTIFIED ON ACCOUNT OF THE GENERAL INTEREST IN PROVIDING WORKERS WITH SOCIAL SECURITY .
11 IN THIS CONNECTION THE LUXEMBOURG INSTITUTION SUBMITS THAT , SINCE THE MEMBER STATES MAY COMPLETELY REFUSE TO ALLOW WORKERS WHO ARE NATIONALS OF NON-MEMBER COUNTRIES TO ENTER THEIR TERRITORY OR TO UNDERTAKE PAID EMPLOYMENT THERE , THEY MAY A FORTIORI ATTACH TO ANY WORK PERMIT WHICH THEY CHOOSE TO GRANT CONDITIONS OR RESTRICTIONS SUCH AS THE COMPULSORY PAYMENT OF THE EMPLOYER ' S SHARE OF SOCIAL SECURITY CONTRIBUTIONS .
12 THAT ARGUMENT CANNOT BE ACCEPTED . A MEMBER STATE ' S POWER TO CONTROL THE EMPLOYMENT OF NATIONALS FROM A NON-MEMBER COUNTRY MAY NOT BE USED IN ORDER TO IMPOSE A DISCRIMINATORY BURDEN ON AN UNDERTAKING FROM ANOTHER MEMBER SATE ENJOYING THE FREEDOM UNDER ARTICLES 59 AND 60 OF THE TREATY TO PROVIDE SERVICES .
13 THE LUXEMBOURG INSTITUTION FURTHER SUBMITS THAT THE APPLICATION OF NATIONAL LEGISLATION