Section 48. A sex offender, as defined by section 178C of chapter 6, who engages in ice cream truck vending, as defined in section 25 of chapter 270, shall be punished by imprisonment in the house of correction for not more than 21/2 years or by a fine of $1,000, or by both such fine and imprisonment. A police officer or officer authorized to serve criminal process may arrest, without a warrant, any person whom he has probable cause to believe has violated this section.