In "Homefront", after Joseph Sisko refuses to submit to a bloodtest, Jake tells his dad he needs to come to the restaurant because "Grandpa's been arrested". When Captain Sisko arrives, he finds Jake and Joseph arguing with the Starfleet officers who were supposed to have been administering the test.
Starfleet, as an exploration/defense organization has always been positioned as analogous to a military force in terms of mission, organization, etc with little authority over civilians. In addition, this takes place before the imposition of martial law. Where, then, do Starfleet officers get the authority to arrest civilians?