In the LAISA cases,66 the European Court of Justice supported the opinion that regulations contained in the accession act are not justiciable under the procedure of Art. 230 E.C. Treaty. It stated that
"this interpretation applies especially as the regulations of the accession act lay down the results of the accession negotiations which are one complex for the solution of those difficulties which the accession brings for the Community as well as the acceding state."
It is true that, if extensive substantive conditions are negotiated especially in relation to the economic, political and legal situation in the acceding states, those are only justiciable to a limited degree.67 However, this does not exclude judicial control as such. The cautious attitude of the European Court of Justice is not based on a specific doctrine limiting judicial power with regard to the content of the deciding questions68 but on the nature of the legal act in question.
According to the international law of treaties, the Member States decide on the contents of treaties they conclude, and it is up to them to change the treaties or to set up new organizational structures. The basis for any binding effect by contract is their collective will, and even a violation of a specific amendment procedure would not lead to the invalidity of the amendment in question.69 However, a treaty amending the E.U. or the E.C. Treaty is, at least, an act of Union or Community law at the same time. If we take the content of a treaty as the relevant factor, we could even argue that its nature is a purely "European" one.
The E.U. Member States have agreed to specific amendment procedures laid down in the E.U.Treaty. As long as their intent is not to modify these procedures or the conditions of amendment, but to act within their framework, the existing legal rules continue to be binding. A violation would, at least, not be in conformity with E.U. law. Furthermore, deciding whether the procedure or the conditions of the amendment have been met would, in any case, not violate the role of the Member States as masters of the treaties - notwithstanding the question whether this role has limits on its own.
Even if there were no general objections to judicial control, it is necessary to look for a legal basis under which the above mentioned question could be brought before the Court of Justice.70 Art. 46 E.U. Treaty states that the powers of the Court of Justice and the exercise of those powers shall apply to the accession procedure set out in the E.U. Treaty. This is a result of the previous situation in which each of the three Community Treaties had a special provision concerning accession and a consequence of the fact that the accession procedure is embodied in the Law of the Union, but it does not serve as a legal basis for judicial control.
On the other hand, it is clear that it is the task of the Court of Justice to ensure the interpretation and application of the Treaties. The question whether the results of accession negotiations violate Union law cannot be decided by any national court. It is true that consideration of Community interests is institutionally secured both by the Commission (as negotiator without a binding role) and by the European Parliament. Still, leaving the control of legal limitations to the Court of Justice would conform to the principle of separation of powers enshrined in the Treaties. Two possible ways remain as a basis for legal protection by the Court:71 First, an action could be brought before the Court against the Council decision, which is necessary in the accession procedure, because the decision is of a binding legal nature (Art. 230 E.C. Treaty). However, it is questionable as to whether this offers effective legal protection. Secondly, there might be a power to decide on the basis of Art. 226 E.C. Treaty, if the co-operation between the Member States in concluding the accession treaty were regarded as a common act falling within the scope of this article. However, this solution would hardly work in practice, because the action can only be brought before the Court by the Commission (or by a Member State, Art. 227 E.C. Treaty).
66 Cases 31 and 35/86, LAISA  ECR 2285/15.
67 See Klein, in: HandKom. EUV/EGV, Art. O EUV, no. 12. Richter, Die Erweiterung der Europäischen Union (1997), p. 161, is against a control of the conditions for an accession by the ECJ.
68 Such as the political question doctrine, see Tribe, American Constitutional Law, vol. I (3rd ed. 2000), § 3-13.
69 See Weiler, The Constitution of Europe (1999), p. 293 et seq.
70 See for the system of legal protection Lenaerts/van Nuffel, Constitutional Law of the European Union (1999), 7-059.
71 A review by means of an opinion seems doubtful. The basis for this would be art. 300 par. 6 E.C. Treaty. Treaties according to this provision are treaties with third states governed by international law where the community acts as a party to the contract. These prerequisites ought not to apply to the Act of Accession.