One of the most important rights.
The meaning of the term “worker" is a matter of European Community law and holds the same meaning in all EU Member States.  The primary feature of an employment relationship is that the employee provides a service in conjunction with the direction of another person for which he or she is paid.  The right to free movement among workers applies within Member States regardless of the purpose of the worker taking up employment in another Member State as long it is not as a means of rehabilitation of the worker into society.  The right to free movement is concerned with both full and part time workers as long as it is significant and not on a marginal scale.
Article 45(4) TFEU states that the Member State authorities have the ability to restrict access to certain posts, in the public service, to nationals. As a result, this exception could potentially limit non-national workers from entering the state. In the case of Sotgiu  the ECJ held that Art 45(4) does not apply to all employment within the public service only certain activities involving the exercise of official authority. It was then in the case of Commission v Belgium  the ECJ laid down the test in determining whether a worker was employed in the public service. It was stated  , “Classification depends on whether or not the posts in question are typical of the specific activities of the public service in so far as the exercise of powers conferred by public law and responsibility for safeguarding the general interests of the State are vested in it."  The ECJ has held that this exception covers posts which involve direct or indirect participation in the exercise of powers within public law which include duties designed to safeguard the general interests of the State. The criteria would then have to be assessed on a case-by-case basis keeping in mind the tasks and responsibilities that are to be covered by the position. Guidance was given in the case of Lawrie-Blum  where the ECJ held that the derogation only applied to those posts which required 'a special relationship of allegiance to the State on the part of the persons occupying them and reciprocity of rights and duties which form the foundation of the bond of nationality.'  These principals were also found in the cases of Commission v France  as well as Allue and Coonan (1989)  . It was in the case of Colegio that the ECJ introduced further limitations on the scope of the Art. 45(4) derogation. It was held that, “The scope of Art 45(4) must be limited to what is strictly necessary for safeguarding the general interests of the Member State concerned..."  It was determined that captains and chief mates  on private-sector ships flying the flag were considered for public exception. The Commission considers that prior case-law must be taken into account when determining which public-sector posts they may reserve for nationals  .
In determining a post to be worthy of protection there should be a standard uniform rule in regards to the public service exception however there is not a standard uniform rule resulting in confusion. The main issue with a uniform rule is the uneven results which could result in different Member States. The ECJ reasoning, at times, has held that most of the posts that are in dispute and have fallen outside the exception stated in Art. 48(4)  . Some of the posts which were accepted were stated during Case 149/79  and included local authority posts for architects, supervisors and some night watchmen, however it is not clear on what basis these posts were so excluded and as a result are these posts really needed to be protected by a public service exception. In the case of Commission v Italy  two functions were covered by the exception, they were the management of public bodies and those advising the State in scientific and technical questions. The second is more explainable due to it being a positions which safeguards the general interest of the state. Positions that were not included in the exception were such things as nurses, local government employees as well as teachers in training.
As it has been suggested, since Commission v Italy, the criteria for public exception remains difficult to interpret. According to Advocate General Mancini  , the test may be whether the public servant exercises a power which affects the position of individuals, however in the modern state this may cover a large amounts of posts. 
Also, the issue of indirect participation in public law powers creates another problem. Any employee of an institution directly exercising public power could be seen as participating indirectly therefore more direct functional link with authority is needs to be shown. The test may look at the task itself and determine if it supports the activity of the individual who exercises it such as secretaries, personal assistants.
The European Court seemed to have difficulties in accepting the second test which involved safeguarding the general interests of the state or other public authorities.  The ECJ accepted that advising of the state on scientific matters could be covered by the exception however it still remains an open to debate on whether educational and cultural interests can be protected. 
Managerial posts in public bodies which do not form part of the central or local administration have also been considered  , but the legal basis for the exercise of powers of management may vary from State to State and between bodies and undertakings so that the application of the criterion may become difficult and arbitrary.
It should be noted that national interests can still be protected through the insisting of satisfying conditions other than nationality. Member States are allowed to implore the possession of national occupational and professional qualifications. General knowledge and linguistic requirements could be imposed to the extent they are necessary for a given post,  however these requirements can not be be made impossible for a non-national to satisfy them.
There is a possibility of derogation under Art. 48(3) and this should not be forgotten but can only be used where an individual's personal conduct justifies this and as a result could never apply to his nationality as such. It can never be applied for economic reasons. 
This led to the question on whether community legislation should be introduced to help clarify the problem and is community legislation necessary to clarify this problem?
When investigating the risks of adding the burden to management to reverse national practice as well as constitutional issues on a national level, it may be deemed to be impractical and a knowledge of the system and a sense of responsibility for the basis of exclusion of non-nationals to the public service.  It is for the states to define how the national interests should be protected and its for the ECJ to arrive at a community solution. Although the commission indicated in 1986 that it was considering the possibility of legislation to make the situation more transparent  it seems increasingly unlikely.
It was in 1988 the commission issued a statement  which laid out a strategy to eliminate restrictions on grounds of nationality and gain access to posts in parts of the public sector. The majority of the statement  contains the Commission's perspectives on what is covered by the exception. It's main purpose was to point out the observations of judge made rules that did not have recourse to new Community legislation  .
The Commission then goes on to look at the second category of protected posts which includes state ministries, local and regional authorities as well as other public bodies. The commission fails to address the issue of what posts involve the “indirect exercise of powers conferred by public law." 
The Commission made note that functions which are considered remote from the specific activities of public service that these exist in the private sector, which Art. 48(4) would not apply, can be completed without the infliction if nationality requirements. It was not that the Commission was looking to exclude a vast range of subordinate posts but instead was trying to see if the posts satisfied the criteria laid out.
In 2010 the Commission made the decision to investigate the current state of play in the national legislation as well as the reforms which have been undertaken and the way the legislation is applied to ensure the right to free movement of workers in the public sector of EU Member States. It was then followed by a article by Professor Ziller which laid out the major sets of issues within the report.
In 2010 Professor Ziller  attempted to identify three major sets of issues, the first being understanding free movement of workers in. Secondly, the public sector; identifying and removing obstacles to free movement of workers in the public sector; and finally understanding the functional approach to Art. 45 (4) TFEU  .
First, understanding free movement of workers in the public sector is difficult due to both vertical and horizontal fragmentation. Workers within the public sector belong to different legal categories making harmonisation difficult.
The next issue is to identify and remove obstacles to free movement of workers in the public sector. What is most often lacking is a provision that establishes or confirms the portability of working periods, i.e. that seniority acquired in EU Member States in situations similar to those which are relevant in the host Member State has to be taken into account on the same footing as professional experience acquired in the host Member State– whether by citizens of other EU Member States or by the host member states own nationals.
Finally, understanding the functional approach to posts reserved to nationals according to Article 45 (4) TFEU  , Art. 45 (4) TFEU provides that “The provisions of this Article shall not apply to employment in the public service"  . The criteria established by the ECJ in order to determine if a post may be reserved to nationals are that a post involves: i) direct or indirect participation in the exercise of public authority and ii) duties designed to safeguard the general interests of the state or of other public authorities  .
It should be noted that in most Member States there have been reforms of public sector employment rules in order to ensure compliance with free movement of workers in the public sector. In some Member States there have also been more specific reforms to legislation and regulations which describe access to public employment and on working conditions in public employment, in order to eliminate obstacles to free movement which had appeared in complaints to the European Commission or in preliminary rulings to the ECJ.
As stated in the report, a standard common statistics that could be assembled and published on a regular basis by for a number of essential indicators. The report goes on to suggests a system where the Member States monitor compliance with EU law with regards to the free movement of workers in the public sector  . Member States would be well advised to establish procedures and organisation for the purpose of ensuring compliance with EU law and the free movement of workers.
It would be in the best interest of the Member States’ authorities to confirm the obligation to taking into account professional experience acquired in other Member State in their legislation and regulations. There must be an effort by Member States in terms of procedural and organisational means in order to achieve mutual recognition of professional experience. It would be useful for Member States to clearly distinguish between professional experience through legislation regulations and practice, or at least in explanatory documents. It would be useful to involve the Committee of the Regions in promoting free movement of workers in the public sector. This would help overcome the problems that have stemmed from horizontal fragmentation of public authorities in the Member State.
This author believes that in order to achieve a complete harmonisation of free movement of workers across Member States the public service exception would have to be deemed unnecessary and through valid arguments, in the report of Professor Ziller, these can be achieved. This would help lead to the goal of complete free movement of workers across Member States. It is important to note that matters of national security still are a sensitive topic for discussion and should be looked at with the utmost care when selecting personnel as well as when drafting legislation. However to have complete free movement between Member States ll aspects of barriers must be abolished.