Yes he can.  But the majority of military police national guard units in my state are composed of the same police men and women that form the police departments in my state.  We see it whenever there are multiple natural disasters; i.e. hurricanes, that impacts communities so badly that cops are victims and national guard has to be deployed. Because those units are filled by off-duty or approved-leave cops from unaffected counties and cities, they can deploy.  But when there are multiple events or communities affected, the NG units aren't always available because the members of the NG military police units are also victims in other communities and demands in that community prevent their use/deployment. If all SO's and PD's in Wisconsin honor the 'no security' plan or call in sick during the convention, you'll have other combat support or combat service support national guard units trying to provide protection and they aren't really well-trained for it. If I was a police union official in Wisconsin, I'd tell the leadership, rank and file to give no indication that they are not going to support the DNC.  They just don't show up once the Convention begins by having a mass 'blue flu' event and it will be a little late to try to organize security once it's happening. Or the minute Antifa, BLM thugs, or any other fascist organizations arrive...or the convention speakers begin advocating for defunding the police, the 'flu' strikes.