Chapter 18
This chapter also starts with that verse:
1 In those days there was no king in Israel. And in those days the tribe of the people of Dan was seeking for itself an inheritance to dwell in, for until then no inheritance among the tribes of Israel had fallen to them. [Jdg 18:1 ESV]
The tribe of Dan still hadn't conquered any land in Canaan for themselves. This MSB note on 18:2:
"On the migration of the tribe of Dan to a new territory, see note on 1:34. Dan was an example of tribal idolatry." The note at 1:34 says Dan failed to secure the land allotted to them and eventually just migrated out of it to another place. There was a story about them capturing a city here in Judges someplace. That city was up in the north, which is where Dan ends up. And now, they will turn to idolatry.
So the tribe sends out five men to find a place they can capture and call their own. They are looking to migrate, rather than to secure the land they were originally allotted. The five stay with Micah. Recognizing that the Levite's accent is all wrong for Ephraim (he was after all from Judah), they inquire who he is. He tells them his story, how this is a personal priest to an individual, leading in idolatrous worship of household gods, and a complete sham and shame and violation of God's word. And upon learning what a travesty this whole situation is, they ask him to inquire of the Lord whether their journey will be successful. As if he could! The priest tells them it will, and they are much encouraged!
From Micah's they go to Laish. They see that it is a rich place, unsuspecting and far from any aid. They go home and get 600 buddies to come with weapons of war to take Laish. The arrive at a location near Micah's house, and the original five relate how there is an ephod, household gods, and a priest at a nearby house, and imply that they might want to think about stealing it as long as they are so close. So they decide now to capture the priest who told them on God's behalf that their mission would be a success. Just twisted beyond believe.
So the 600 steal the carved and metal images, the Ephod, and essentially, the priest. They convince him to be a priest for the whole tribe of Dan rather than for just one man. He goes with them. So in this way, the tribe of Dan turns completely to idolatry, looking to an apostate Levite to lead them in worshiping idols built to celebrate the return of money stolen by a son from his own mother. How could this possibly turn out badly for Dan?
When the owner finds out, he and the neighbors go after the thieves. But they taunt him, and realizing he really can't do anything, Micah goes back home. The story reads like they stole his livestock and slaves and so on in addition to the religious stuff.
The Danites continue to Laish, burn it down, rebuild it and move in. This verse about Laish and its people:
27 But the people of Dan took what Micah had made, and the priest who belonged to him, and they came to Laish, to a people quiet and unsuspecting, and struck them with the edge of the sword and burned the city with fire. [Jdg 18:27 ESV]
These people were sitting around, comfortable with what they had, living peaceful lives. You just cannot do that. There will always be some who want to take what you have. We are to always be prepared.
So now Dan has a place to live. They set up the gods of Micah, and establish Jonathan son of Gershom son of Moses as their priest. Things remain this way until Israel is captured. They worship these idols while the Tabernacle is still in Shiloh. So they are 100% in violation of Mosaic law.