OF ALL the people stoking the pressure on Germany’s chancellor these days, the most relentless is Horst Seehofer, Bavaria’s premier and leader of its governing party, the Christian Social Union (CSU). Angela Merkel’s refugee policy, he said this week, amounts to a “reign of injustice”—or “illegality”, depending on the translation. This month he will decide whether Bavaria will sue the federal government in the constitutional court in Karlsruhe.

The argument that Mrs Merkel’s “welcome culture” is not only naive but downright illegal is popular among German conservatives. Proponents include eminent jurists such as Hans-Jürgen Papier, a former president of the constitutional court (and a member of the CSU). Claiming asylum in Germany is technically impossible for anybody arriving on a land route, he points out. Under the German constitution, since an amendment in 1993, protection is not available to people entering from “safe” states, a description that fits all nine of Germany’s neighbours.

European Union law brings him to the same conclusion. The EU’s so-called Dublin agreement stipulates that refugees must claim asylum in the first member state they reach. Geographically, this cannot be Germany, unless refugees take an aeroplane or ship. Mr Papier concedes that Dublin has broken down. But while it allows Germany to process asylum claims voluntarily, it does not oblige it to. Given the magnitude of the crisis—with 1.1m refugees arriving in Germany last year—such a decision would have to be made by parliament rather than Mrs Merkel. Since the Bundestag has never yet voted on her overall policy, Mr Papier calls it “quasi-legal”. Another former judge on the constitutional court, Udo di Fabio, goes a step further. Approached by Bavaria for a legal opinion on the suit, he concluded that it could win. His argument—which will sound more familiar to Americans than to citizens of more centralised states—is based on German federalism.