In this article we perform an economic analysis of different regulatory frameworks that aim at guaranteeing solidarity in competitive health insurance markets. Thereafter, we analyse the legal conformity of these intervention strategies with EC law. We find that risk compensation schemes are the first-best intervention strategy because they guarantee an ‘acceptable level of solidarity’ without hindering free trade and competition and without reducing efficiency. Second-best options are premium and excess-loss compensation schemes, which guarantee solidarity at the expense of some efficiency. Premium rate restrictions and open enrolment should be avoided because they reduce efficiency and are unnecessary, not proportional, and undesirable to the pursuit of the general good. These conclusions are relevant for EU countries that adopt premium rate restrictions and open enrolment in combination with a risk compensation scheme, such as Ireland and the Netherlands. In these countries policy makers should design the health insurance schemes in conformity with EC law, for example by replacing premium rate restrictions and open enrolment with premium and/or excess-loss compensation schemes.