If' I'm BP and the goverment is threatening my assets with seizure, then my PR machine goes into high gear. Remember, I have three trillion in sales per year and I can eat a one-time $20B his and still make $10B in profits. Here's what I say:

"We're prepared to set up a multi-billion dollar fund to pay claims in the Gulf so that the residents of that area won't have to go through what the people of Alaska had to endire - but the government is threatening an unconstitutional seizure of assets (see Ammendment 5 of the Constitution) which would prevent us from focusing on these efforts."

Now, if there were threats that were not nearly as drastic, I'm guessing we wouldn't hear of them. But nationalizing foreign assets? That would get the government of the UK involved and I can't imagine the kind of furball that would start happening.