Check the U.S. FAR regs. There's an exception for exceeding 250 KTS if your clean minimum manuevering speed is above 250 KTS.
In the U.S. there is no waiver of the 250 KTS below 10,000 except for emergencies or military a/c(pre approved, we used to fly 300 or 350 KIAS below 10,000 in the IFR traffic flow).
If there are published maximum speeds on SIDS/STARS, absent relief by ATC, you stay configured, if necessary, until past the speed constraint.