On what grounds of Canon law would they do this?
Support for unlimited abortion by aiding and abetting the election of the most antilife president in American history.
The election of Obama will lead to the passage of FOCA, and millions more lives will be lost to abortion.
Excommunication applies not only to those who actively perform abortions, but to those who aid and assist in any way. This applies to all pro-abortion politicians,and those who helped them get elected.