There is a growing body of research on the impact of the electoral system "ballot structure" on the behaviour of politicians. We offer a clear, ordinal, and rules-based three-way coding (closed, flexible, open) of the electoral systems used in European Parliament elections, taking into account both the ballot type and the intra-party seat-allocation rules. For the notoriously difficult group of flexible list-systems, we show how these operated in the 2004, 2009 and 2014 elections, and introduce an additional behavioural distinction between "weakly flexible" and "strongly flexible" subtypes at the party-list-level. We then illustrate how the type of ballot used in an election can influence individual policy representation by looking at the vote-splits between MEPs in the European People's Party in a vote on tackling homophobia.