Brazilian excommunication warning
The city policy is, in my opinion, unquestionably wicked and immoral (CCC 1910, 2273, 2377). But whether those who use, or incite the use of, this pill are committing an excommunicable offense depends on, among other things (e.g., 1983 CIC 1323-1324, 1329), whether an abortion is actually procured thereby (1983 CIC 1398).
If the 'morning after pill' works by preventing ovulation, it is contraceptive; if it works by preventing implantation, it is abortifacient. Only the latter, but certainly the latter, provides a basis in canon law for excommunication. See my blog post "Excommunication for deliberate embryo destruction" (29 June 2006). +++
See also my Excommunication Blotter, updated regularly.