Free movement of workers within the EU
Let us begin by noting that that Article 39(4) is one of two exceptions to the free movement of workers within the EU. The other is Article 45 EC, according to which those self-employed persons who "exercise official authority" also may not move freely interstate between posts of employment. (Kaczorowska, 2008) There is not always a clear distinction to be drawn between the two articles except that under Article 45 EC those who carry out official state business "occasionally" are disqualified from freedom of movement, whilst under Article 39(4) the worker must act in an official capacity, exercising some aspect of sovereign authority, on a regular basis. Both laws have, as is noted by various writers (Kaczorowska, 2008; Pieter van der Mei, 2003; Smith, 2008) been only restrictively interpreted by the ECJ. Article 39(4) – to return to our main point of discussion – has been ruled only to apply to employment access. As Apap (2002) quotes the ECJ:
This provision cannot justify discriminatory measures with regard to remuneration or other conditions of employment against workers once they have been admitted to the public service. The very fact that they have been admitted shows indeed that those interests which justify the exception to the principle of non-discrimination... are not at issue.
What is vague or problematic about the way in which Article 39(4) is that it has been exceptionally difficult to come to a consistent interpretation of it in a way which is not simply meted out by the ECJ. The reason for this is of course obvious: in a law which deals with an interstate matter, inconsistency of interpretation would cause problems. The ECJ gave a definition of what counts as the kind of post that would count as an exception in the case of Commission v. Belgium,  in which Belgium challenged a number of decisions about those professions cast as exceptions. Under Article 39(4), for a post to fall under the exception it has to
Involve direct or indirect participation in the exercise of powers conferred by public law and duties designed to safeguard the general interests of the State or other public authorities... Such posts in fact presume on the part of those occupying them that the existence of a special relationship of allegiance to the State and reciprocity of rights and duties which form the foundation of the bound of nationality. 
There is of course still a great deal of vagueness even in this case. The notion of "a special relationship of allegiance to the State" and "direct and indirect participation" are defined not only with looseness, but perhaps even with a certain degree of incoherence. The notion that Article 39(4) attempts to enshrine is one which forms an ideological core to EU employment law: that the functions that it attempts to identify are those which require "a special relationship of allegiance to the state on the part of the persons occupying them and the reciprocity of the rights and duties which form the foundation of the bond of natonality." These terms, however, although they sound rich with the portent of foundational principle, are in fact terribly ambiguous. The case law suggests that there is in fact a list chosen on the basis of the cases discussed which demarcates the professions required – and there is even a hint that it would be better if the cases were decided domestically. But here we find incoherence.
After all, the rest of the Articles of 39 EC seem to leave room for a number of professions which are very broadly construable as being in the National Interest. Take the example of Ankar, Ras & Snoek v Germany.  In the court’s opinion, the scope could not be extended to the access of a certain fishing boat which flew the German flag. (Bogaert, 2003) It was emphasised, in keeping with the ruling in Commission v Belgium, but with heavier emphasis, that Article 39(4) must be "limited to the what is strictly necessary for safeguarding the general interests of the Member Srare concerned, which would not be imperilled if the rights under powers conferred by public law were exercised only sporadically... by nationals of other Member States." 
As Blanpain (2008) notes, what was eventually decided was that the EC would allow Member States to reserve the right to give the top posts of flag-flying merchant ships just when those shops have certain law-given powers. It was (Apap 2002 remarks) concluded that commercial enterprises generally – even those as central to the working of a state as "public transport, post and telecommunications and supplies of electricity and gas" should not be included as falling under Article 39 (4). (Apap 2002: 50) This is because, as ECJ put it, they are "too remote from the specific activities of public service because they do not involve direct or indirect participation in the exercise of powers conferred by public law..."  The Commission has found Greece guilty of having protected such posts in areas such as education, healthcare, utilities, public transport, post and telecommunications, radio and television broadcasting, etc..; whilst Luxembourg was "condemned for maintaining posts for its own nationals in public sectors of research, education, health, inland transport, post, telecommunications, and the utilities to its own nationals." (Both points owed to Bernard, 2007: 2210)
Quite apart from anything else, it is clear that the exception for public service workers needs to be uniformly interpreted by the member states, and it is therefore not possible, at least not a priori, for us to understand how this would be possible without an ECJ interpretation from above. Although various states in the name of national interest (Luxembourg, for example, arguing that it needed its teachers to be nationals because they were imbuing the younger generation with Luxembourgian values – Bernard, 2007) there are a widely divergent set of attempts to take advantage of the change in the law. It is difficult to see how it would be possible for any kind of law to be effective in maintaining certain positions as excepted from the general laws about the freedom of movement simply through the "increased closeness of the Member States."
Having said that, there are of course problems and inconsistencies with the ECJ interpretation of Article 39(4) that we have not yet identified. From the cases discussed above, a pattern emerges: this pattern is that the Article 39(4) exception really only applies to high-level public services jobs. It is on the basis of this emergent fact that one can argue with a degree of justifiability that there is a case to be made for doing without Article 39(4) altogether. After all, if it us only among the higher echelons of public services that there is any need even to consider this law, then there are already provisions in place which allow Article 27(3) of the EC it is possible to apply to the home member state of a potential employee and enquire whether he or she poses any risk to national security. the employer to ignore certain aspects of EU law in order to preserve national security - indeed there is no law to prevent a state allowing access to lower echelon. The issue with this is it is that once an employee is employed in a state service, there is no provision within Article 39(4) for that employee to then be excluded on the basis of nationality. And there is a clear inconsistency here. There has, Apap (2002) points out, been attempts to get around this inconsistency. In Commission v Italy there was a move to argue that even if a post was not presently qualified for the exception under Article 39(4), the fact that later career promotions might qualify the worker give reason enough to exclude him or her in the first place.  But the ECJ argued that in these cases it was up to the Member State itself to restrict certain posts just to foreign nationals. In Commission v Luxembourg this judgement was confirmed, and it was further stipulated that there should be no blanket exclusions allowed on entire professions simply because of the status of higher echelons.
This does not, however, really deal with the problem. We are left with something like a regress: there is on the one hand the clear fact that the ECJ needs to decide from above as to which posts can be included under Article 39(4). It is also clearly stipulated that the rule is only about access, and not promotion. There are two consequences for this. The first is that the ECJ requires Member States to treat promotions as "new jobs" which is evidently to defeat the point of its failing to say anything about promotions in the first place. Article 39(4) is not simply about access; it also makes prescriptions about internal promotion as well. And second, there seems to be a clear sense in which a paradox of definiton of post emerges. We have already seen the difficulty of a Member State’s using Article 39(4) to serve nationalist ends which do not fit with the generally centre-right bent of the EC. But if the matter of protected posts is (as ECJ suggests at times) decided domestically in particular with regard to which level of a post may be subjected to the exception, then matters become confusing. There is no longer a clear basis in authority or in the case law.
On the other hand, that is not to say that it would be better or more effective to have no exception at all, unless a desideratum is the creation of a European super state in which the best public service workers migrate to the country which offers the highest bid. Lacroix (2010) suggests that the notion of a super state is strange, given that the EU defines the notion of the "postmodern state" – it has "embraced as their guiding principles... cooperation, mutual interference, and a heightened sense of morality in international affairs." What is strange about this is twofold. To begin with, it is strange that that the crux of the issue with respect to Article 39(4) is that it is neither in keeping with this ideal of the EU, nor is it in keeping with the old-fashioned Modern State (a la Russia or USA). It occupies a middle ground where the need for homogeneity is felt, but in practice the difficulty encountered in achieving it is partly due to a strict desire to adhere to an ideology of national self-identity. What it comes down to, perhaps, is a matter of trust.
In this essay we have seen a number of things. We have seen that the public service exception is a slippery Article: it is vague enough to require canonical ECJ hermeneutic treatment, which is then passed down biblically to member states. Evidence for this comes in the fact that there are a large number of inconsistencies (as we have seen in the case law) in the way individual states understand it. There is clearly also great potential for its being used to serve ideological ends that are at odds with the overriding goals of the EU. That, however, is not to say that the closeness of the EU renders the Article unnecessary – quite the contrary. Although it may be clumsy and lead to misunderstanding, without any stipulation regarding the movement of workers the EU would be placed in a much worse bind. Disagreements over ideology would be magnified through the dissonance between the liberality of one country over another. Although one cannot predict the effects of this, for the matter to go smoothly a level of equality between Member States would have to be much greater than it is currently. What seems the best course of action, until the EU develops into a superstate (!) is to carry out significant claraficatory work; to create, as far as possible, a list of positions which constitute those which fall under Article 39(4). Although such a list cannot be comprehensive, and will be continually added to as the case law develops, it would still be better than attempting vaguely and ambiguously to define the matter a priori.