This will be brief. In an old essay on the topic, we see this:
"...Catholic legislators who are members of the faithful of the Diocese of La Crosse and who continue to support procured abortion or euthanasia may not present themselves to receive Holy Communion. They are not to be admitted to Holy Communion, should they present themselves, until such time as they publicly renounce their support of these most unjust practices" (canon 915).
That was from now-Cdl. Burke when he reigned as Bishop of LaCrosse. Note the red-highlighted part which makes it clear that it IS the obligation of a priest to DENY the Sacrament to those who 'support procured abortion'. (There are other reasons besides that and euthanasia, of course.)
We're sure that Bp. Callahan, now in LaCrosse, is aware of this.