I trade on Schwab and TDA. I have traded in at least 5 CE stocks for buys on Schwab this month. I have only tried TDA with GBDX and it was restricted. Due to the fees TDA charges for penny stocks, I usually don't trade them there. Just did a test on GBDX which I have no trouble buying or selling on Schwab.
EDIT have done buys with Schwab for these CE plays DBMM, ECCI, PMDP, SFIN,GBDX, TRAE.
The government was set to protect man from criminals - and the Constitution was written to protect man from the government. - Ayn Rand
Jim