No he can't! You are really out in left field on how transactions and the block chain work.
Sorry , but you have no clue what you talk about.
Somebody who has 51% of the hash rate can make any coins out there useless because he can deny all the transactions from that address.
Google a bit , it would help
I can confirm this, to make it simple: your transactions are still relayed on the network, true, but if 90% of the miners (through their pool) are excluding your transactions from their mined blocks, AND they reject, as part of the conspiracy, every block mined from foreign nodes (that would confirm your tx's), then...
tl;dr: yes your coins can be embargoed completely quite "easily" by someone with 90%.