Several central European leaders whom I have met mop their brows when the topic is mentioned. Most of them refer to that inspiring topic, the Common Agricultural Policy. Many politicians and officials from the applicant countries have found many specific parts of it either unsuitable for their own needs or objectionable in principle. But they are reluctantly accepting it as the price of membership that they value for political reasons. This may be part of the reason why one adviser to a central European government said that negotiating with the EU reminded her of negotiating with the nomenklatura in the old Soviet Union.
Some lawyers seems to think subsidiarity is applicable only to future developments.
It does not therefore affect what has gone before. In fact, however, acquis communautaire concerns existing members of the EU, and not only applicant countries. For it does tend to entrench the status quo and place an obstacle in the way of those who would like to repatriate aspects of policy, such as the Common Agricultural Policy, to the national states. Strictly speaking, a piece of EU legislation can be repealed or amended just like a French or British or US law. But it is a much more difficult and cumbersome process at the European level.