(I haven't used SOAP::Lite for a long time, so just guessing.)

Looking at lib/SOAP/Lite.pm, it seems that stuff is probably done by new using register_ns. Offhand I don't see a clean way to "unregister" a namespace, but the way register_ns is implemented -- if you just want to get on with life and don't mind dirty hacks -- it looks like you could do something like (untested) delete $soap->{_namespaces}{soapenc} for example to remove soapenc.