Catalysis of the reaction: 4-deoxy-beta-D-gluc-4-enuronosyl-(1->3)-N-acetyl-D-galactosamine 4-sulfate + H2O = 4-deoxy-beta-D-gluc-4-enuronosyl-(1->3)-N-acetyl-D-galactosamine + H+ + sulfate.
4-deoxy-beta-D-gluc-4-enuronosyl-(1,3)-N-acetyl-D-galactosamine-4-sulfate 4-sulfohydrolase activity