Technically, yes, if your nodes have a conflicting transaction. If you broadcast too many invalid transactions/nodes to a few nodes, they will note that you are a misbehaving peer and will disconnect you. However, you won't be banned from the entire network, just a few nodes.
If you are working on a transaction broadcasting service, you should implement checks to see if the transaction is valid and no other conflicting transaction is in your mempool.
okie., will do that.
so there is no global node ban list ? something like that ?
how can i check if the tx_hex is valid ?
i guess by decoding hex and checking the inputs and outputs. ?
As far as I know, there is no global list.
You can check validity by decoding it, as you mentioned, and then compare it to what you have in the mempool. If the inputs were already spent in your mempool, then there's something fishy going on...