He can sign an “executive agreement” but then he can only order the executive branch to honor it. The rest of the country is free to ignore it. The military enters into “executive agreements” with foreign governments every week. But these agreements only require the military to be bound. In order to enforce some carbon tax scheme, he would have to go the treaty route. Congress would not enact implementing legislation for an executive agreement.
Putting aside the technicalities, China will not go for this in any form. Particularly if ObaMao sighs this travesty, the Chicoms will stop backing our loans and I predict a large sell off of treasury securities will occur.
China may also demand they get paid immediately what they are owed, knowing the American economy and financial system will go under rapidly because of the effects that this will have on the entire American industrial sector.
China will then become the largest industrial power and the financial and stocks market will shift to Asia.