WWE came armed with a legal order that was signed several days ago that allowed them to seize any material sold within 5 miles of Wrestlemania. That's a standard tactic that touring acts do to prevent bootleg t-shirts being sold outside their events. Since Wrestlecon fell within that perimeter, WWE came by to see what was being sold.
Those who had material seized were given a court date to appear and try to argue their case as to why the material should be returned...and risk paying damages. WWE took personal information of those who were selling materials.
WWE came armed with a massive list of their copyrights and trademarks to show they were being infringed upon.