These bishops may well be wrong, but they are not "the church". The bishops' conference does not have the ability to define doctrine. Gun regulation is a temporal matter subject to the prudential judgement of the voters and their representatives. The bishops can express their opinion on matters such as these, but (unlike topics related to faith and morals such as abortion and euthanasia) these opinions are non-binding on the laity.
My inalienable rights are not subject to the voters or their representatives in any way, shape, or form.