In America abortion is a battleground. Pro-lifers urge the Supreme Court to overturn Roe v Wade, its convoluted ruling in 1973 that made abortion legal in all states. Pro-choice campaigners fret that, one day, they will succeed. Presidential elections hinge, in part, on the kind of judges each candidate vows to appoint. And test cases crop up regularly. This week the Supreme Court heard arguments for a law making it harder to run abortion clinics in Louisiana, which could lead to the closure of two of the three in that state.