Quite correct. The president has all the legal firepower he needs to grab BP assets. All it would take would be for the DOJ to seek an emergency court hearing, present evidence of a crime committed (ample in this case) and seek appointment of a federal receiver over selected BP assets. For starters: all BP's federal offshore leases. In which case, BP's best defense would be to pre-emptively file for Chapter 11 protection.
A further note: federal receivers are not required to follow the same mandates as bankruptcy judges. Their job is to make whole the government and taxpayers. Shareholders, bondholders and other trade creditors could be left in the dust by a receiver. BTW, shed no tears for the Brits. Since BP took over Amoco and ARCO in the 1990s, a majority of its shares have been held by US citizens or institutions.