After repeatedly intoning "Scotland will not be disrespected by this Parliament," Bercow ordered the SNP's London leader to depart the chamber.
In response, Blackford called for the House to sit in private, in order to disrupt proceedings. If successful, his demand would've disrupted parliament for 15 minutes — the call was a mechanism for forcing a vote on clearing the private gallery.
The leader's protest stemmed from Scotland's treatment in the Brexit negotiations, and the EU withdrawal bill in particular.
Bercow said he would take it at the end of the parliamentary session, and told Blackford to resume his seat. Blackford refused, so he was ordered to leave — when he departed, his fellow parliamentarians left with him.