The umpire should have made the players take them off. A player is not allowed to were anything that would be deemed as dangerous to any other player as well as there one self (see rule 4.3 Uniforms and 4.4 other equipment)
4.4.2 Players shall not wear equipment (objects) that may cause injury to other players.
" The following are not permitted:
¬ Finger, hand, wrist, elbow or forearm guards, casts or braces made of leather, plastic, pliable (soft) plastic, metal or any other hard substance, even if covered with soft padding.
¬ Objects that could cut or cause abrasions (fingernails must be closely cut).
¬ Headgear, hair accessories and jewellery.
FIBA International basketball (2004) "Official Basketball Rule" as viewed at http://www.basketball.net.au/_uploads/res/1_23577.pdf As approved by FIBA Central Board